In interactive (user) contexts, use `try_sign` instead of `sign`.
We also revisit the `Profile` by adding a `signer` method that can
fail, eg. if we couldn't connect to ssh-agent.
Finally, we replace `UnsafeSigner` with `MemorySigner`, which makes
use of `ssh::Keystore`.
Signed-off-by: Alexis Sellier <alexis@radicle.xyz>
To build an address book, peers communicate via gossip, sending
`NodeAnnouncement` messages.
These need to be handled by storing the addresses in an address book
and the addresses need to be persisted to disk.
Node announcement messages should also be relayed to peers like other
gossip messages.
Dr. Maxim Orlovsky
Alexis Sellier