Weird things that were merged too fast with #1040:

• What happens if self.federated_only and self._identity_evidence is NOT_SIGNED? Currently, the method simply finishes without returning a value (hence, returning None).
• The logic for decentralized validation is the following:

            # Off-chain signature verification
            if self._stamp_has_valid_wallet_signature():
                self.verified_stamp = True
                return True

            # On-chain staking check
            if verify_staking:
                self._is_valid_worker()

It seems that the on-chain checks are never hit when self._stamp_has_valid_wallet_signature(), since it returns True. Or conversely, the only way to do the on-chain check is to fail the stamp's signature verification, which is wrong.

In any case, I'm working in #1033 in alhambra-verde and I'll fix this too.