[REQ] Kotlin generators should support generation of value class if applicable

[orolhawion]

Is your feature request related to a problem? Please describe.

It would make code safer and easier to read if a Kotlin generator would support the generation of value classes if applicable.

See https://kotlinlang.org/docs/inline-classes.html for Kotlin value class details

Describe the solution you'd like

This might be an optional setting which probably needs to be defined in the generator config. I could not find anything in openapi itself that would suggest that value classes are supported.

If an openapi defined object has one single attribute of a primitive type (+String), a value class can and should be generated. The name should be derivable from the openapi definition.

    Street:
      type: object
      required:
        - name
      properties:
        name:
          type: string
          description: "The name of the street as part of an address"

could be generated as

@JvmInline value class Street(val name: String)

What do you think?