[Ruby] Components that use allOf are broken

Using the allOf keyword in the OpenAPI YAML file causes the generator to create broken classes.

 $ swagger-codegen version
 > 3.0.26

Consider the components in the following YAML file:

openapi: 3.0.3
info:
  title: Test
  version: 0.0.1
components:
  schemas:
    SimpleThing:
      type: object
      properties:
        prop1:
          type: string
    ComplexThing:
      allOf:
        - $ref: "#/components/schemas/SimpleThing"
        - type: object
          properties:
            prop2:
              type: string
paths:
  /ping:
    get:
      responses:
        '200':
          description: OK
          content:
            text/plain:
              schema:
                type: string

Running swagger-codegen creates two model classes. SimpleThing, which doesn't inherit, looks fine:

simple_thing.rb

module SwaggerClient
  class SimpleThing # <- Does not extend anything
    def initialize(attributes = {})
      # Nothing weird in here
    end
  end
end

ComplexThing looks like it wants to inherit SimpleThing, but does not:
complex_thing.rb

module SwaggerClient
  class ComplexThing # <- Does not extend anything
    def initialize(attributes = {})
      # ...

      # call parent's initialize
      super(attributes) # <---- This line fails with "ArgumentError (wrong number of arguments (given 1, expected 0))"

      # ...
    end
  end
end

The end result is that using the Ruby client to connect to any endpoint which returns a ComplexThing will fail with an ArgumentError.

I believe this is somewhat related to https://github.com/swagger-api/swagger-codegen-generators/pull/856, except the fix there was to remove the arguments in super, whereas the right fix here might be to have subclasses extend correctly.

Reproduce the issue with the supplied OpenAPI YAML and Swagger Codegen 3.0.26, then compare the generated simple_thing.rb and complex_thing.rb files. Trace the Ruby model-generation path for allOf and verify that ComplexThing correctly inherits from SimpleThing and can initialize without the reported ArgumentError.