Malformed ticket validation requests (also if date(time) is malformed) should be 400 instead of 403

If we encounter an malformed date in a ticket validation request we return 403. What some groups expect is 400 which does make sense but the api technically only defines 403 and 200 as valid responses.

Task: Determine if we should return 400 or 403 in this case. Take appropriate action ☑

New api clearly states that it should be 400.

Task: Change response for malformed ticket validation requests (also if date(time) is malformed) to be 400 instead of 403.