Send "not typing anymore" notifications more #4811
Description
When the user is typing a PM, we send typing-status notifications.
The semantics is that these expire naturally: if the user keeps typing, we keep sending them periodically, and if a client on the other end sees a timeout interval (15 sec, I think) go by without getting another, then it considers the user no longer typing.
But there are also situations when the user has actively stopped typing. For those, the API supports a "not typing anymore" notification, which causes the receiving client to cancel the "Greg is typing…" display immediately.
Currently we handle one of these situations: when the user sends their message. This works by invoking the sendTypingStop thunk action.
We should do the same thing in several more situations:
- when the user blurs the compose box, i.e. when it loses focus because the user has interacted with something else in the UI;
- when the user navigates away to some other screen -- either by navigating back, or by navigating forward to somewhere else;
- when the user clears the whole contents of the compose box.