Changes to create engine session

added the media type application/json for the response with the status 503

added the new optional request property sessionOptions/dataRetention

added the new optional request property sessionOptions/egress

added the new optional request property sessionOptions/sessionReplay

added the new optional request property sessionOptions/showAIAvatarDisclosure

added the new optional request property sessionOptions/videoHeight

added the new optional request property sessionOptions/videoQuality

added the new optional request property sessionOptions/videoWidth

added the non-success response with the status 404

added the non-success response with the status 409

added the optional property invalid_fields to the response with the 400 status

added the media type application/json for the response with the status 400

added the new optional request property environment/livekitUrl

added the non-success response with the status 402

added the new optional request property sessionOptions/region

added the new optional request property sessionOptions/regionPolicy

added the media type application/json for the response with the status 403

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

endpoint added