Add NetworkBridgeEvent::UpdatedAuthorityIds

[Szegoo]

Closes: #6192

[Szegoo]

@rphmeier I would just like to confirm that I understand the issue correctly. As mentioned we want to introduce UpdatedAuthorityIds to the NetworkBridgeEvent. We should track for authority id updates inside the network bridge subsystem and dispatch the NetworkBridgeEvent::UpdatedAuthorityIds if authority ids are updated, right?

I am not sure for which network event should we check and emit the UpdatedAuthorityIds, I hope you could clarify this for me.

[Szegoo]

@rphmeier Could you PTAL.

[ordian]

Some thoughts with my understanding:

• Key rotations will lead to a rather quick DHT update, which means that authority discovery cache might be updated soon after. get_authority_ids_by_peer_id method should return both old authority_id and the new one after the update.
• However, on chain the changes will take place on the new session only.

The only problem here seems to be statement-distribution maintains an additional mapping AuthorityId -> PeerId which is only updated on peer connection/disconnection, so it will not take into account session rotations.

Since it's a only becomes a problem on session rotations, we could issue this message in gossip-support on each new session.

[Szegoo]

@ordian I think the PR should be feasible now, if I am not wrong, I think I implemented all of the necessary logic for the UpdatedAuthorityIds to work.

[ordian]

Thanks!

[Szegoo]

@ordian Could you approve the PR if the changes are ok?

[Szegoo]

@bkchr Could you review this?

[ordian]

@Szegoo sorry for the delay! Could you merge recent master?

[Szegoo]

Could you merge recent master?

Done.

[rphmeier]

Looks good - some guide changes would be nice too!

Sorry, I completely forgot about this PR.

Doing this check every session is a good step. Probably all we'll need. But more frequent checks may be needed in the future.