title: Swagger codegen to Java Spring generates incorrect file response entity from OpenAPI component of binary format
body: <p>I am using swagger-codegen-maven-plugin to generate  Spring interface from OpenAPI file (OpenAPI 3.0.2)</p>
  
  <pre><code>&lt;groupId&gt;io.swagger.codegen.v3&lt;/groupId&gt;
  &lt;artifactId&gt;swagger-codegen-maven-plugin&lt;/artifactId&gt;
  &lt;version&gt;3.0.14&lt;/version&gt;
  </code></pre>
  
  <p>The response of one rest API should be PDF file</p>
  
  <pre><code>components:
      schemas:
          contractFile:
              type: string
              format: binary
  </code></pre>
  
  <p>Generated Java REST interface then contains the following method</p>
  
  <pre><code>default ResponseEntity&lt;File&gt; getContract(@ApiParam(value = "File to download",required=true) @PathVariable("uid") String uid) {
  ...
  }
  </code></pre>
  
  <p>File class represents the path to the filesystem, but I don't have the file on the filesystem, just bytes in java memory and I don't want to save them as the file to disk.</p>
  
  <p>I want getContract to return some StreamResource or some other representation of file from Stream/bytes in memory. Is it possible this via swagger-codegen-maven-plugin or some other option?</p>