CLICS allowes another format

We should also allow:
yyyy-mm-ddThh:mm:ss(.uuu)?[+-]zz(:mm)?
besides
yyyy-mm-dd hh:mm:ss(.uuu)?[+-]zz(:mm)?
          ^
See: https://github.com/icpc/ccs-specs/blame/master/Contest_API.md#L233

Author: vmcj

webapp/src/Validator/Constraints/TimeStringValidator.php

@@ -11,7 +11,7 @@ class TimeStringValidator extends ConstraintValidator
     public function validate(mixed $value, Constraint $constraint): void
     {
         $timezoneRegex = "[A-Za-z][A-Za-z0-9_\/+-]{1,35}"; # See: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
-        $absoluteRegex = "\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d(\.\d{1,6})? " . $timeZoneRegex;
+        $absoluteRegex = "\d\d\d\d-\d\d-\d\d( |T)\d\d:\d\d:\d\d(\.\d{1,6})? " . $timeZoneRegex;
         $relativeRegex = "\d+:\d\d(:\d\d(\.\d{1,6})?)?";
         if (!$constraint instanceof TimeString) {
             throw new UnexpectedTypeException($constraint, TimeString::class);