Add apis to update the account relays.

[delcin-raj]

Implement,

1. add relay
2. remove relay

This should handle 3 different relay types for an account.

NOTE:

Discovery relays should not be published as NIP-65 event.
The Inbox and key package relays update must be published to discovery relays with the correct event type.

[jgmontoya]

Is this issue still relevant after this PR: #296 ??

[delcin-raj]

Closing it