[REQ] openapi-generator-maven-plugin oneOf support

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

We have following JSON Schema

{
  "$id": "https://example.com/some.schema.json",
  "title": "some",
  "type": "object",
  "properties": {
    "id": {
      "type": "string"
    },
    "someEnum": {
      "type": "object",
      "oneOf": [
        {
          "properties": {
            "businessId": {
              "const": "001"
            },
            "name": {
              "const": "first"
            }
            ...
          },
          "required": ["businessId", "name"]
        },
        {
          "properties": {
            "businessId": {
              "const": "002"
            },
            "name": {
              "const": "second"
            }
          },
          "required": ["businessId", "name"]
        }
      ]
    }
  },

  "required": ["id", "someEnum"]
}

Describe the solution you'd like

It would be nice supporting generation of "someEnum". At the moment it is simply empty class

Describe alternatives you've considered

https://github.com/joelittlejohn/jsonschema2pojo/issues/1193

Start by tracing the openapi-generator-maven-plugin path that processes the supplied JSON Schema and its oneOf definition. Compare the generated result for someEnum with the schema alternatives and identify how generation is currently verified. Done means the plugin generates a useful someEnum model instead of an empty class, with coverage for the shown oneOf structure.