The only situation that isn't working yet is sending `left` events for
users when the sender leaves the room

feat: first steps towards joining rooms over federation
Add state-res as a dependency of conduit
Add reverse_topological_power_sort before append_pdu
Implement statehashstatid_pduid tree for keeping track of state
Clean up implementation of state_hash as key for tracking state

The only situation that isn't working yet is sending `left` events for
users when the sender leaves the room

Use if let instead of unwrap

Default to invalid password if could not calculate

Move hash password methdo and return Result

Rename get_password method

Default to empty password when no pwd is received

Store hashed passwords

Store passwords hashed with Argon2 and verify password with that stored
hash.

Co-authored-by: Guillem Nieto <gnieto.talo@gmail.com>

PDUs are saved in a pduid -> pdus map. roomid -> pduleaves keeps track
of the leaves of the event graph and eventid -> pduid maps event ids to
pdus.