Changes to Contract Refund

the response's body type changed from object to no type for status 500

the success response's property type changed from boolean to string for status 200

removed the required property success from the response with the 500 status

removed the required property success_message from the response with the 500 status

added OASSchemaOnlySuccessFailureResponse OASSchemaOnlyAPIExceptionResponse to the response body anyOf list for the response status 500

added the non-success response with the status 409

added the non-success response with the status 429

added the optional property error_code to the response with the 200 status