Remove type hints from comments which have been added
as Python type hints. This helps avoid drift between comments
and reality, as well as removing redundant information.
Also adds some missing type hints which were simple to fill in.
Part of the Tchap Synapse mainlining.
This allows modules to implement extra logic to figure out whether a given 3PID can be added to the local homeserver. In the Tchap use case, this will allow a Synapse module to interface with the custom endpoint /internal_info.
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>`
* [ ] split config options into allowed_local_3pids and registrations_require_3pid
* [ ] simplify and comment logic for picking registration flows
* [ ] fix docstring and move check_3pid_allowed into a new util module
* [ ] use check_3pid_allowed everywhere
@erikjohnston PTAL
