title: OpenApi generator generates spring boot 2 server controller interface with incorrect(?) Flux / Mono response types
body: <p>I'm trying to generate controller interface with Flux / Mono types(I'm doing refactor to WebFlux).</p>
  <p>Here is my openapi spec part:</p>
  <pre><code>/api/courses:
      get:
        tags:
          - RestCourse
        summary: Provides all courses
        operationId: getAll
        responses:
          '200':
            description: OK
            content:
              application/json:
                schema:
                  type: array
                  items:
                    $ref: '#/components/schemas/ApiCourse'
  </code></pre>
  <p>Part of pom.xml:</p>
  <pre><code>&lt;plugin&gt;
                  &lt;groupId&gt;org.openapitools&lt;/groupId&gt;
                  &lt;artifactId&gt;openapi-generator-maven-plugin&lt;/artifactId&gt;
                  &lt;!-- RELEASE_VERSION --&gt;
                  &lt;version&gt;6.0.1&lt;/version&gt;
                  &lt;!-- /RELEASE_VERSION --&gt;
                  &lt;executions&gt;
                      &lt;execution&gt;
                          &lt;goals&gt;
                              &lt;goal&gt;generate&lt;/goal&gt;
                          &lt;/goals&gt;
                          &lt;configuration&gt;
                              &lt;inputSpec&gt;${project.basedir}/src/main/resources/openapi.yaml&lt;/inputSpec&gt;
                              &lt;generatorName&gt;spring&lt;/generatorName&gt;
                              &lt;!--&lt;templateDirectory&gt;${project.basedir}/templates&lt;/templateDirectory&gt;--&gt;
                              &lt;configOptions&gt;
                                  &lt;dateLibrary&gt;java8&lt;/dateLibrary&gt;
                                  &lt;!--&lt;useSpringController&gt;true&lt;/useSpringController&gt;--&gt;
                                  &lt;interfaceOnly&gt;true&lt;/interfaceOnly&gt;
                                  &lt;sourceFolder&gt;src/java/main&lt;/sourceFolder&gt;
                                  &lt;modelPackage&gt;spring.learn.api.model&lt;/modelPackage&gt;
                                  &lt;apiPackage&gt;spring.learn.api.controller&lt;/apiPackage&gt;
                                  &lt;useTags&gt;true&lt;/useTags&gt;
                                  &lt;unhandledException&gt;true&lt;/unhandledException&gt;
                                  &lt;openApiNullable&gt;false&lt;/openApiNullable&gt;
                                  &lt;reactive&gt;true&lt;/reactive&gt;
                                  &lt;!--&lt;library&gt;spring-boot&lt;/library&gt;--&gt;
                              &lt;/configOptions&gt;
                          &lt;/configuration&gt;
                      &lt;/execution&gt;
                  &lt;/executions&gt;
              &lt;/plugin&gt;
  </code></pre>
  <p>Generated result is:</p>
  <pre><code>default Mono&lt;ResponseEntity&lt;Flux&lt;ApiCourse&gt;&gt;&gt; getAll(...
  </code></pre>
  <p>But i think should be:</p>
  <pre><code>default Flux&lt;ResponseEntity&lt;ApiCourse&gt;&gt; getAll(...
  </code></pre>
  <p>Or I'm wrong?</p>