url static method
Checks a web address (http/https optional). UValidators.url()
Implementation
static FormFieldValidator<String> url({String? requiredMessage, String? invalidMessage, bool isRequired = true}) => (String? value) {
if (isRequired && (value == null || value.isEmpty)) return requiredMessage ?? U.s.required;
if (value != null && value.isNotEmpty && !value.isValidUrl) return invalidMessage ?? U.s.thisFieldIsInvalid;
return null;
};