Creates a new implementation-specific endpoint for accepting
confirmation of password resets. This endpoint should be hit with the
same parameters as the regular password reset submit_token endpoint.
This endpoint will now complete the password resets, whereas the
existing endpoint will now just show the confirmation template page.

…sword_reset_confirmation

* 'develop' of github.com:matrix-org/synapse: (22 commits)
  Update the test federation client to handle streaming responses (#8130)
  Do not propagate profile changes of shadow-banned users into rooms. (#8157)
  Make SlavedIdTracker.advance have same interface as MultiWriterIDGenerator (#8171)
  Convert simple_select_one and simple_select_one_onecol to async (#8162)
  Fix rate limiting unit tests. (#8167)
  Add functions to `MultiWriterIdGen` used by events stream (#8164)
  Do not allow send_nonmember_event to be called with shadow-banned users. (#8158)
  Changelog fixes
  1.19.1rc1
  Make StreamIdGen `get_next` and `get_next_mult` async  (#8161)
  Wording fixes to 'name' user admin api filter (#8163)
  Fix missing double-backtick in RST document
  Search in columns 'name' and 'displayname' in the admin users endpoint (#7377)
  Add type hints for state. (#8140)
  Stop shadow-banned users from sending non-member events. (#8142)
  Allow capping a room's retention policy (#8104)
  Add healthcheck for default localhost 8008 port on /health endpoint. (#8147)
  Fix flaky shadow-ban tests. (#8152)
  Fix join ratelimiter breaking profile updates and idempotency (#8153)
  Do not apply ratelimiting on joins to appservices (#8139)
  ...

Co-authored-by: Richard van der Hoff <[email protected]>

To correctly emulate a POSTed URL-encoded form submission from the browser, we
needed to do a few things.

* URL-encode the request arguments and place their 'key=value' pairs, separated
  by '&' characters, into a byte string.
* Place this byte string in the request body instead of the query parameters.
* Set the request's 'Content-Type' header to
  'application/x-www-form-urlencoded', instead of 'application/json', which was
  previously the default when making a request in the unit tests.

Additionally, @clokep noticed that we needed to seek to the end of the request
content before passing it to twisted, else things blew up.

They are now simply GET vs POST /submit_token. Thanks to @richvdh for the idea.

This commit also removes the endpoint from handling .../msisdn/... calls, as
Synapse currently doesn't support handling password resets via this medium.

There shouldn't be any cases where it is called.

…sword_reset_confirmation

* 'develop' of github.com:matrix-org/synapse: (39 commits)
  Fix errors when updating the user directory with invalid data (#8223)
  Explain better what GDPR-erased means (#8189)
  Convert additional databases to async/await part 3 (#8201)
  Convert appservice code to async/await. (#8207)
  Rename `_get_e2e_device_keys_txn` (#8222)
  Convert additional databases to async/await (#8199)
  Convert the well known resolver to async (#8214)
  Convert additional databases to async/await part 2 (#8200)
  Make MultiWriterIDGenerator work for streams that use negative stream IDs (#8203)
  Do not install setuptools 50.0. (#8212)
  Move and rename `get_devices_with_keys_by_user` (#8204)
  Rename `get_e2e_device_keys` to better reflect its purpose (#8205)
  Add a comment about _LimitedHostnameResolver
  Convert ReadWriteLock to async/await. (#8202)
  Fix incorrect return signature
  Fix `wait_for_stream_position` for multiple waiters. (#8196)
  Convert `event_push_actions`, `registration`, and `roommember` datastores to async (#8197)
  Only return devices with keys from `/federation/v1/user/devices/` (#8198)
  Convert state and stream stores and related code to async (#8194)
  Ensure that the OpenID Connect remote ID is a string. (#8190)
  ...

…org/synapse into anoa/password_reset_confirmation

* 'anoa/password_reset_confirmation' of github.com:matrix-org/synapse:
  Update UPGRADE.rst
  Switch from an unstable /_matrix/client prefix to /_synapse/client
  Combine the submit_token and submit_token_confirm endpoints
  Convert confirmation from request args to HTML form data
  Return 400 when accessing submit_token/_confirm with REMOTE behaviour
  Pull things from, instead of copying the entirety of, the config
  Update synapse/rest/client/v2_alpha/account.py

…sword_reset_confirmation

We needed to switch the admin import as else it tries to import relatively, and
we end up importing the wrong module.