When API response is a MAP, the generated API interface does not contain import java.util.Map;

Description

When API response is a MAP, the generated API interface does not contain import java.util.Map;

Swagger-codegen version

tested with 2.2.3, 2.3.0 and 3.0.0

Swagger declaration file content or url

swagger: '2.0'

info:
  version: 0.0.0
  title: Following yaml generates an interface that has a missing import

paths:
  /testingMapResponse:
    get:
      produces:
        - application/json
      parameters:
        - name: clientID
          in: query
          required: true
          type: string
          minLength: 2
          maxLength: 4
      responses:
        200:
          description: Response is a map
          schema:
            title: Testing
            type: object
            description: This should be a map (<String, List<String>).
            additionalProperties:
              type: array
              items:
                type: string
                minLength: 3
                maxLength: 25
        400:
          description: Invalid Request Submitted
          schema:
            $ref: '#/definitions/APIErrors'
        404:
          description: Not found
          schema:
            $ref: '#/definitions/APIErrors'


definitions:
  APIErrors:
    description: a list of errors
    type: array
    items:
      $ref: '#/definitions/APIError'

  APIError:
    description: Error information
    type: object
    properties:
      message:
        description: a text description describing the error
        type: string

Related issues/PRs

This issue seems to be similar to https://github.com/swagger-api/swagger-codegen/issues/2937

Suggest a fix/enhancement

I can submit a PR if you point me on the right direction?

Start by reproducing the generated Java API interface with the Swagger 2.0 YAML in the issue, focusing on the response schema using additionalProperties. Trace how the generator determines imports for that response type; done means the generated interface includes java.util.Map and compiles across the reported versions.