READ lets downstream clients share information between each other about
what messages have been read by other downstreams.
Each target/entity has an optional corresponding read receipt, which is
stored as a timestamp.
- When a downstream sends:
READ #chan timestamp=2020-01-01T01:23:45.000Z
the read receipt for that target is set to that date
- soju sends READ to downstreams:
- on JOIN, if the client uses the soju.im/read capability
- when the read receipt timestamp is set by any downstream
The read receipt date is clamped by the previous receipt date and the
current time.
Make Network.Nick optional, default to the user's username. This
will allow adding a global setting to set the nickname in the
future, just like we have for the real name.
References: https://todo.sr.ht/~emersion/soju/110
This is a mecanical change, which just lifts up the context.TODO()
calls from inside the DB implementations to the callers.
Future work involves properly wiring up the contexts when it makes
sense.
