Previously, the bot only had rudimentary typing notification support.
It used to send a single notification when starting a long task
and did not bother with notifications anymore.
By default matrix-rust-sdk gives these notifications a validity of 4
seconds, so it would expire shortly. If the bot takes longer to respond,
you'd see the typing notification expire and wonder if a response is
coming.
Another edge case is the bot sending an answer quicker and the typing
notice still being on. Some clients (like element-web) seem to hide the
typing notice when a new message comes, so they don't experience this as
problematic.
The reworked typing notification system should be robust:
- typing notices are sent continuously, until the bot finishes doing
work
- if the bot is performing multiple actions in a room (even for
different people), typing notices would continue to be sent until the
bot becomes idle
- as soon as the bot becomes idle, a "not typing anymore" notice is sent
to clear the state
