- Use `client` instead of `profile`
- Add `decrypt_value_by_profile` which is notably useful on client startup, when the
encrypted password needs to be retrieved, and the `SatXMPPEntity` instance is not yet
created.
- Add type hints/update docstrings
rel 477
Priority was historically set to 50 to follow behaviour of other clients at the time, but
it's nowadays a legacy feature, and a non zero value can cause trouble if message carbon
is not used.