title: openapi-generator-maven-plugin adds quotes to enumeration and swagger-ui uses them causing error
body: <p>We have service defined like:</p>
  <pre><code>openapi: &quot;3.0.0&quot;
  info:
    version: 1.0.0
    title: UVZ Reg
  paths:
    /enumerationRequestApproval/{requestId}/{approvalStatus}:
      post:
        tags: 
          - EnumerationApprovalController
        parameters:
         - in: path
           name: requestId
           schema:
             type: integer
             format: int64
           required: true
         - in: path
           name: approvalStatus
           schema:
             $ref: &quot;#/components/schemas/enumerationApprovalStatusEnum&quot;
           required: true
        responses:
          200:
            description: status of enumeration approval changed
  components:
    schemas:
      enumerationApprovalStatusEnum:
        type: string
        enum:
          - WAITING_APPROVAL
          - APPROVED
          - NOT_APPROVED
  </code></pre>
  <p>With help of openapi-generator-maven-plugin we generate spring boot service:</p>
  <pre><code>@javax.annotation.Generated(value = &quot;org.openapitools.codegen.languages.SpringCodegen&quot;, date = &quot;2020-07-30T09:35:26.969160+02:00[Europe/Bratislava]&quot;)
  
  @Validated
  @Api(value = &quot;enumerationRequestApproval&quot;, description = &quot;the enumerationRequestApproval API&quot;)
  public interface EnumerationRequestApprovalApi {
  
      default Optional&lt;NativeWebRequest&gt; getRequest() {
          return Optional.empty();
      }
  
      /**
       * POST /enumerationRequestApproval/{requestId}/{approvalStatus}
       *
       * @param requestId  (required)
       * @param approvalStatus  (required)
       * @return status of enumeration approval changed (status code 200)
       */
      @ApiOperation(value = &quot;&quot;, nickname = &quot;enumerationRequestApprovalRequestIdApprovalStatusPost&quot;, notes = &quot;&quot;, tags={ &quot;EnumerationApprovalController&quot;, })
      @ApiResponses(value = { 
          @ApiResponse(code = 200, message = &quot;status of enumeration approval changed&quot;) })
      @RequestMapping(value = &quot;/enumerationRequestApproval/{requestId}/{approvalStatus}&quot;,
          method = RequestMethod.POST)
      default ResponseEntity&lt;Void&gt; enumerationRequestApprovalRequestIdApprovalStatusPost(@ApiParam(value = &quot;&quot;,required=true) @PathVariable(&quot;requestId&quot;) Long requestId,@ApiParam(value = &quot;&quot;,required=true, allowableValues = &quot;\&quot;WAITING_APPROVAL\&quot;, \&quot;APPROVED\&quot;, \&quot;NOT_APPROVED\&quot;&quot;) @PathVariable(&quot;approvalStatus&quot;) EnumerationApprovalStatusEnum approvalStatus) {
          return new ResponseEntity&lt;&gt;(HttpStatus.NOT_IMPLEMENTED);
  
      }
  
  }
  </code></pre>
  <p>Now when we try to call service from swagger-ui (http://localhost:8080/swagger-ui) it will fail:</p>
  <pre><code>org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@io.swagger.annotations.ApiParam @org.springframework.web.bind.annotation.PathVariable sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum] for value '&quot;WAITING_APPROVAL&quot;'; nested exception is java.lang.IllegalArgumentException: No enum constant sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum.&quot;WAITING_APPROVAL&quot;
      at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:133)
      at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
      at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:167)
      at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134)
      at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
      at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at sk.uvzsr.is.reg.config.CorsFilter.doFilter(CorsFilter.java:43)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
      at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
      at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
      at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
      at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1594)
      at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
      at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
      at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
      at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
      at java.base/java.lang.Thread.run(Thread.java:830)
  Caused by: org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@io.swagger.annotations.ApiParam @org.springframework.web.bind.annotation.PathVariable sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum] for value '&quot;WAITING_APPROVAL&quot;'; nested exception is java.lang.IllegalArgumentException: No enum constant sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum.&quot;WAITING_APPROVAL&quot;
      at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:47)
      at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:191)
      at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:129)
      at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:73)
      at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:53)
      at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:693)
      at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:125)
      ... 50 more
  Caused by: java.lang.IllegalArgumentException: No enum constant sk.uvzsr.is.reg.be.rest.model.EnumerationApprovalStatusEnum.&quot;WAITING_APPROVAL&quot;
      at java.base/java.lang.Enum.valueOf(Enum.java:266)
      at org.springframework.core.convert.support.StringToEnumConverterFactory$StringToEnum.convert(StringToEnumConverterFactory.java:52)
      at org.springframework.core.convert.support.StringToEnumConverterFactory$StringToEnum.convert(StringToEnumConverterFactory.java:38)
      at org.springframework.core.convert.support.GenericConversionService$ConverterFactoryAdapter.convert(GenericConversionService.java:436)
      at org.springframework.core.convert.support.ConversionUtils.invokeConverter(ConversionUtils.java:41)
      ... 56 more
  </code></pre>
  <p>It is clear problem is with quotes around enumeration value. When I changed</p>
  <pre><code>allowableValues = &quot;\&quot;WAITING_APPROVAL\&quot;, \&quot;APPROVED\&quot;, \&quot;NOT_APPROVED\&quot;&quot;)
  </code></pre>
  <p>to</p>
  <pre><code>allowableValues = &quot;WAITING_APPROVAL, APPROVED, NOT_APPROVED&quot;)
  </code></pre>
  <p>everything works, but since it is generated API I cannot change it manually every time.</p>
  <p>This is how API looks while in design (no quotes):
  <a href="https://i.stack.imgur.com/gWJwB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gWJwB.png" alt="API shown in Visual studio plugin, without quotes" /></a>
  This is how API looks deployed (quotes added):
  <a href="https://i.stack.imgur.com/ZVXh4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZVXh4.png" alt="API shown in deployed swagger-ui, with quotes" /></a></p>
  <p>I tested this with</p>
  <ul>
  <li>openapi-generator-maven-plugin version 4.2.3 and 4.3.1.</li>
  <li>springfox-swagger-ui 2.9.2 and 3.0.0 (springfox-boot-starter maven artifact)</li>
  </ul>
  <p>Is this problem with openapi-generator-maven-plugin, swagger-ui or my OpenApi3 definition? How can I fix this to work?</p>