fix: libp2p records for ipns should be signed

[vasco-santos]

There are two types of IPNS records. IPNS records for being stored locally and IPNS records for being used in the network.

IPNS records for being stored locally are used for understanding which is the most recent record since it is stored by the peer who published it.

IPNS records for being used in the network, are used as a common libp2p-record and are intended to be used with the DHT and Pubsub.

This way, the libp2p-record should have a signature and that signature should be validated on the resolve, in order to guarantee that the record was not changed in the network.

NOTE: The current implementation guarantees that the IPNS Record is not changed, since it has its own signature, but the libp2p-record used must be used as a generic libp2p-record, with its own signature as well.

[alanshaw]

Can you please explain why this is necessary? Seems as though serializeSigned does the same as serialize, but has the side effect of setting a signature property on the record. The record is then discarded, so all that appears to be happening is just verifying that is can be signed without error.

UPDATE: I take that back the signature property is set before serialize() is called so the signature is included in the serialized record.

[vasco-santos]

@alanshaw edited the initial description of the PR. Does it make sense to you now?

[alanshaw]

LGTM. I have rebased for you and just waiting on CI again now.