* fix(ap): add safe constructors, getters, and validators to ActivityPub actors to address #4701
* chore: replace nil check with the new Validate() method
* chore(test): added test to verify the values extracted from actors
* fix: return the specific error type + test for it
* fix(ap): add recovery for each AP inbox worker for a worst case scenario
* fix(ap): add additional safe accessor methods to other AP entities other than actors
* chore(tests): add tests for the new safe accessors
* fix(ap): handle empty public keys in AP actors
