isAfter method Null safety
Check if the value (a Date) is after the given Date.
Implementation
static String? isAfter(String? value, {String? message, required min}) => value == null || value.isEmpty || validations.isAfter(value, min) == true
? null
: message ?? 'Please enter a date after ${min.runtimeType.toString() == 'DateTime' ? min.toString().substring(0, 10) : min}';