IntroduceIdentityPage: Use new size limit constant for puzzle IDs
IntroduceIdentityPage: Don't process request in constructor, do it in make() as we do it everywhere else
IntroduceIdentityPage: Don't use deprecated API
- Replace with getPartAsStringThrowing() instead of *Failsafe() because it doesn't make any sense to process IDs/solutions which are cut off beyond the length limit.
- Don't swallow UnknownPuzzleException so when testing the changes we will notice whether the change of ID processing broke things.