[BUG][kotlin-spring] "SwaggerAnnotations=true" leads into compile error when using inheritance

Created by: d0x

Description

When using inheritance, the generated code won't compile. It fails with this error:

This annotation is not applicable to target 'member property without backing field or delegate'

You can see it in this example:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "animalType", visible = true)
@JsonSubTypes(
      JsonSubTypes.Type(value = Pet::class, name = "Pet")
)
interface Animal{
                @ApiModelProperty(example = "null", value = "")
                // ^^^^^^^^^^^^^^^^^^^ This annotation is not applicable to target 'member property without backing field or delegate'
        val weight: java.math.BigDecimal? 
}

openapi-generator version

Generator Version 4.0.3 Spec Version 3.0.1

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  title: example
  version: 1.0.0
paths:
  /test:
    get:
      responses:
        200:
          description: successful operation
components:
  schemas:
    Animal:
      type: object
      properties:
        weight:
          type: number
      discriminator:
        propertyName: animalType
      required:
        - animalType
    Pet:
      allOf:
        - $ref: "#/components/schemas/Animal"
        - type: object
          properties:
            name:
              type: string

Command line used for generation

openapi-generator generate -i myspec.yml -g kotlin-spring \
        -Dmodels \
        -Dapis \
        --additional-properties=interfaceOnly=true \
        --additional-properties=gradleBuildFile=false \
        --additional-properties=exceptionHandler=false \
        --additional-properties swaggerAnnotations=true \
        --additional-properties=sourceFolder=src/gen/kotlin

Steps to reproduce

Generate the spec above and check the Animal class.

Related issues/PRs

There is another issue related to inheritance: