Support for Custom OpenAPI Schema Extensions in Udash REST

[mwrona-avs]

Please add support for custom schema extensions in the Schema object in Udash REST, as outlined in the OpenAPI specification: Specification Extensions.

If a generic solution that allows any field is not feasible, please consider adding predefined schema extensions for enums, such as:

• x-enum-varnames
• x-enum-descriptions

Reference for enum extensions: OpenAPI TS Enum Extensions.