Changes to Create a new world generation job

the input/oneOf[subschema #2]/image_url request property format changed from uri to starts_with

the webhook/url request property format changed from uri to starts_with

the request property model became required

the model request property's minLength was increased from 0 to 1

added the new ply enum value to the request property output_format

removed subschema #6 from the input request property oneOf list