Multiple anyOf implementations not supported

Description

My model has multiple anyOf implementations, however in any Codegen generator only the 'last' one is created as an interface.

Swagger-codegen version

3.0.14

Swagger declaration file content or url

openapi: 3.0.0
info:
  title: Sample Double Interface
  version: 0.0.1
paths:
components:
  schemas:
    PartOne:
      properties:
        name:
          type: string
          description: A test description
    PartTwo:
      properties:
        id:
          type: string
    PartThree:
      properties:
        otherId:
          type: string
    PartFour:
      properties:
        otherIdPart:
          type: string
    PartMaster:
      properties:
        origin:
          anyOf:
            - $ref: '#/components/schemas/PartThree'
            - $ref: '#/components/schemas/PartFour'
        otherOrigin:
          anyOf:
            - $ref: '#/components/schemas/PartThree'
            - $ref: '#/components/schemas/PartFour'

Command line used for generation

swagger-codegen generate -c java-generator-opts.json -i model/test.yaml -Dmodels --template-engine handlebars -l java

Suggest a fix/enhancement

I think whatever is building the map is using the same key

Start with model/test.yaml and java-generator-opts.json, then run the reported swagger-codegen generate command for the Java generator. Compare the generated representations of origin and otherOrigin, checking whether both anyOf implementations are retained rather than only the last one. Done means both properties generate the expected interfaces.