json_body is used in places that need authentication. In
case an unknown field is set, Ruma doesn't parse the field
and so doesn't give an error on invalid UTF-8. But Conduit
has parsed and on error makes json_body None. Return an
error to the client instead of generating an internal error.

- get encryption keys over federation
- optimize signing key storage
- rate limit parsing of bad events
- rate limit signature fetching
- dependency bumps

TIL body.device_id != (*body).device_id, which is pretty bad, so I
renamed body.device_id to body.sender_device

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