[ASPNETCORE] readOnly property $ref type is not resolved when model is generated

Description

data type is not resolved properly for readOnly model properties if $ref is used

Swagger-codegen version

2.4.5

Swagger declaration file content

category property was marked as readOnly and I need to use allOf to set data type reference using $ref

  Pet:
    title: a Pet
    description: A pet for sale in the pet store
    type: object
    required:
      - name
      - photoUrls
    properties:
      id:
        type: integer
        format: int64
      category:
        readOnly: true
        allOf:
          - $ref: '#/definitions/Category'

Command line used for generation

java -jar .\modules\swagger-codegen-cli\target\swagger-codegen-cli.jar generate -i modules\swagger-codegen\src\test\resources\2_0\petstore.yaml -l aspnetcore -o samples\server\petstore\aspnetcore\ --additional-properties packageGuid={3C799344-F285-4669-8FD5-7ED9B795D5C5}

however this requires Pet.category to be updated in the petstore.yaml

Steps to reproduce

• modify petstore.yaml according to Swagger declaration file content
• run command from Command line used for generation
• Category property in the Pet model has unresolved Object data type

Related issues/PRs

Suggest a fix/enhancement

DefaultCodegen.getSwaggerType method does not check ComposedProperty inner properties.

Start with DefaultCodegen.getSwaggerType and inspect how it handles ComposedProperty inner properties. Reproduce the issue by updating petstore.yaml with the readOnly category and running the provided ASP.NET Core generation command. Done means the generated Pet.category property resolves to Category instead of Object.