Tracks presence on an individual per-device basis and combine
the per-device state into a per-user state. This should help in
situations where a user has multiple devices with conflicting status
(e.g. one is syncing with unavailable and one is syncing with online).
The tie-breaking is done by priority:
BUSY > ONLINE > UNAVAILABLE > OFFLINE
Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
- Update black version to the latest
- Run black auto formatting over the codebase
- Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
- Update `code_style.md` docs around installing black to use the correct version
