[BUG][KOTLIN] object type should not generate property of type "Any"

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When using a property of type "object" the generated code uses Kotlin type "Any" which is incorrect. This is because this would allow setting the property to any value on Kotlin side - for example a string. Setting the value to a string is though not in bounds of the given type in the spec, as an "object" should always be a list of properties and their values.

I would expect that using a type "object" generates a Map<String, Any?> as type in Kotlin instead.

openapi-generator version

7.7.0

OpenAPI declaration file content or url

openapi: 3.1.0
info: 
  title: ""
  version: 1.0.0
paths: {}
components:
  schemas:
    SomeNiceClass:
      type: object
      properties:
        someValue:
          type: object

Generation Details

Language: Kotlin

Steps to reproduce

No special steps needed, just generate the model for the spec above.

Related issues/PRs

None - or at least I couldn't find one.

Suggest a fix

I can only tell that the generator for Go does this correctly and generates a map[string]interface{} for type "object".

Start by generating the Kotlin model from the issue's minimal OpenAPI 3.1 declaration and inspect the generated type for SomeNiceClass.someValue. Compare the result with the requested Map<String, Any?> representation and add or update the relevant Kotlin generator coverage if the project has it. Done means an object property no longer generates as Kotlin Any while the reproduction remains valid.