[Spring] application/octet-stream generate an Objetc File instead of byte[]

Swagger-codegen version

V 3.0.2

Description

I was using swagger 2.0 with mavenplugin-codegen V 2.3.1 :
When i have a response type application/octet-stream
=> Json file : "schema" : { "type" : "string", "format" : "binary"}
=> Genetares this signature in the Interface API:
@RequestMapping(value = "/addressbooks/export/{addressBookId}", produces = { "application/octet-stream" }, method = RequestMethod.GET)
public ResponseEntity<byte[]>

Now i have migrated in openApi3 with mavenplugin-codegen V3.0.2
When i have a response type application/octet-stream
=> Json file : "content":{"application/octet-stream":{"schema":{"type":"string","format":"binary"}}}
=> it generates this signature Interface API :
@RequestMapping(value = "/addressbooks/export/{addressBookId}",produces = { "application/octet-stream", "application/json" }, method = RequestMethod.GET)
default ResponseEntity< File >

The fact that the response is a File instead of byte[] makes spring raise this exception :
"org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation"

Steps to reproduce

1. Create a openAPi3 with this response :
   responses:
   '200':
   content:
   application/octet-stream:
   schema:
   type: string
   format: binary

2. Generate the Json file.

3. Launch the build with codegen 3.0.2 for spring

4. Check you have a signature => default ResponseEntity< File >

5. Try to reach this endpoint

6. Must get: "org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation"

Related issues/PRs

Suggest a fix/enhancement

Start by reproducing the Spring generator output from the OpenAPI 3 response schema shown in the issue using swagger-codegen 3.0.2 and the Maven plugin. Trace the generated endpoint signature and its response handling; done means an application/octet-stream response generates a usable byte[] representation instead of File and no longer raises the reported media-type exception.