title: OpenAPI generator: wrong format for the example value of date datatype. Is it possible to customize?
body: <p>I am using <strong>openapi-generator</strong> of the latest version (<strong>4.2.2</strong>) for generation of Java Spring API. Configuration looks like this:</p>
  
  <pre><code>openApiGenerate {
      generatorName = "spring"
      inputSpec = "${projectDir}/src/main/resources/api/users-spec.yaml"
      outputDir = "${buildDir}/generated/open-api"
      apiPackage = "com.example.accounts.api"
      invokerPackage = "com.example.accounts.handler"
      modelPackage = "com.example.accounts.model"
      modelNameSuffix = "Json"
      configOptions = [
              delegatePattern: "true"
      ]
  }
  </code></pre>
  
  <p>I found out that definitions containing datatypes of <code>date</code> with example values produce differently formatted values in the output Java models.</p>
  
  <pre><code>definitions:
    User:
      properties:
        birthday:
          description: Date of birth
          type: string
          format: date
          example: "2020-01-01"
  </code></pre>
  
  <p>The generated model is: </p>
  
  <pre><code>  @ApiModelProperty(example = "Wed Jan 01 03:00:00 MSK 2020", value = "Date of birth")
    @Valid
    public LocalDate getBirthday() {
      return birthday;
    }
  </code></pre>
  
  <p>After the creation of swagger ui with <strong>springfox (2.9.2)</strong> I am having an example request as <code>{"birthday": "Wed Jan 01 03:00:00 MSK 2020"}</code>. It is confusing because a standard Jackson date deserializer cannot deserialize such value. Can I have an example value in <strong>yyyy-mm-dd</strong> format?</p>