create method
Implementation
void create({required UContentCreateParams p}) => UServices.content.create(
p: p,
onOk: (UResponse<String> r) => okCallback(r.message, read),
onError: (UEmptyResponse r) => errorCallBack(r.message, read),
onException: (String e) => errorCallBack(U.s.errorSubmittingForm, read),
);