[CSharp] Objects with only inherited properties are not generated

[rima1098]

Describe the bug

When a schema (object) only inherits properties from a base object and does not have own properties then the corresponding C# class is not generated and on the Base object no JsonInheritanceAttribute is generated.

I tried to circumvent this by setting an additional Attribute on BaseObject with the objectType: ObjectA, however, it turns out that a stackoverflow occurs when trying to write a BaseObject.

Eventhough ObjectA in general equals the BaseObject, it might still be necessary for the API to know wheter it receives ObjectA or only a BaseObject.

Version used

14.2.0

To Reproduce

generate C# Client in Nswag Studio with the default settings and the following specification:

openapi: 3.0.0
info:
  title: test
  description: test
  version: 0.0.0

paths:
  /test:
    post:
      operationId: test
      requestBody:
        content:
          'application/json':
            schema:
              $ref: '#/components/schemas/BaseObject'
      responses:
        '200':
          description: "OK"
        
components:
  schemas:
    BaseObject:
      type: object
      required:
        - objectType
        - prop1
      properties:
        objectType:
          type: string
        prop1:
          type: string
      discriminator:
        propertyName: objectType
          
    ObjectA:
      allOf:
        - $ref: '#/components/schemas/BaseObject'
        
    ObjectB:
      allOf:
        - $ref: '#/components/schemas/BaseObject'
      properties:
        prop2:
          type: string
  

Expected behavior

A C# Class for Object A should be generated like:

public class ObjectA : BaseObject ...

A JsonInheritanceAttribute should be generated on the Base Object:

[Newtonsoft.Json.JsonConverter(typeof(JsonInheritanceConverter), "objectType")]
[JsonInheritanceAttribute("ObjectB", typeof(ObjectB))]
[JsonInheritanceAttribute("ObjecA", typeof(ObjectA))]
[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "14.2.0.0 (NJsonSchema v11.1.0.0 (Newtonsoft.Json v13.0.0.0))")]
public partial class BaseObject