[BUG] Kotlin retrofit: binary response missing import

Created by: ghost

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Having a binary response, leads to a missing import with jvm-retrofit2 library. The ResponseBody import is missing.

openapi-generator version

5.1.0

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: Test
  version: 1.0.0
paths:
  /image:
    get:
      responses:
        '200':
          description: Event image in JPEG format
          content:
            image/jpeg:
              schema:
                type: string
                format: binary

Generation Details

openapi-generator generate -i spec.yaml -g kotlin --library jvm-retrofit2

Steps to reproduce

1. Generate code from spec
2. Check missing import in DefaultApi.kt:

package org.openapitools.client.apis

import org.openapitools.client.infrastructure.CollectionFormats.*
import retrofit2.http.*
import retrofit2.Call
import okhttp3.RequestBody

// MISSING: import okhttp3.ResponseBody
interface DefaultApi {
    /**
     * 
     * 
     * Responses:
     *  - 200: Event image in JPEG format
     * 
     * @return [Call]<[ResponseBody]>
     */
    @GET("image")
    fun imageGet(): Call<ResponseBody>

}

Suggest a fix

Update the api.mustache: Add

{{#operation}}
{{#isResponseFile}}
import okhttp3.ResponseBody

{{/isResponseFile}}
{{/operation}}

at the bottom of the imports section (line 50).