fix(server): non-nullable IsOptional (#3939)

* custom `IsOptional`

* added link to source

* formatting

* Update server/src/domain/domain.util.ts

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

* nullable birth date endpoint

* made `nullable` a property

* formatting

* removed unused dto

* updated decorator arg

* fixed album e2e tests

* add null tests for auth e2e

* add null test for person e2e

* fixed tests

* added null test for user e2e

* removed unusued import

* log key in test name

* chore: add note about mobile not being able to use the endpoint

---------

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

mobile/openapi/test/person_update_dto_test.dart

@@ -16,7 +16,7 @@ void main() {
   // final instance = PersonUpdateDto();
 
   group('test PersonUpdateDto', () {
-    // Person date of birth.
+    // Person date of birth. Note: the mobile app cannot currently set the birth date to null.
     // DateTime birthDate
     test('to test the property `birthDate`', () async {
       // TODO