Support automatic re-authentication for Sessions

[ecton]

After a good discussion with @daxpedda, we want to implement a "resume session" feature to allow re-establishing sessions after a configurable amount of time. We can also enable session reconnection at the TLS level both in http and fabruic which would alleviate the need protocol-level session resuming. However, I think a combination of both approaches is ideal.

The TLS-level implementation can be transparent, but there is limited ability to customize the behavior on a per-connection or per-identity basis. Protocol-level session resuming could allow different identities the ability to resume connections for longer periods of time.

The protocol-level implementation would generate new tokens periodically that the client can send back on reconnect to resume a recently disconnected session. If the server honors the token, the session can be resumed on the Client without reporting a disconnection error or unauthenticated error.

Originally posted by @ecton in #264 (comment)