[Java] [Retrofit2] Generator do not tolerate Enums as body parameters

Description

While Retrofit2 allows @retrofit2.http.Body List<Enum> bodies, the generator creates @retrofit2.http.Body List<String>.

Swagger-codegen version

2.3

Swagger declaration file content or url

/users/{userId}/roles:
    put:
      operationId: updateUserRoles
      parameters:
        - name: userId
          in: path
          required: true
          type: string
        - in: body
          name: roles
          schema:
            type: array
            minItems: 0
            items:
              type: string
              enum: [SUPERUSER, TUTOR, STUDENT]
      responses:
        200:
          description: User roles have been updated

Generated retrofit2 + rx2 client code:

  @PUT("users/{userId}/roles")
  Completable updateUserRoles(
    @Path("userId") String userId, @Body List<String> roles
  );

Should be

  @PUT("users/{userId}/roles")
  Completable updateUserRoles(
    @Path("userId") String userId, @Body List<RolesEnum> roles
  );

Start by reproducing the Retrofit2 + Rx2 client generation with the Swagger declaration in this issue, then trace the generator templates or entry points that produce the updateUserRoles signature. Done means an enum type such as RolesEnum is retained for the array body parameter instead of String.