Don't crash on lack of expiry templates

Add some endpoints for account validity management

Send out emails with links to extend an account's validity period

Make sure we're not registering the same 3pid twice

Remove usage of request.postpath

VersionRestServlet doesn't take a param

This is an undocumented variable in twisted, and relies on the servlet
being mounted in the right way.

This also breaks getting push rules on workers.

* Use packages.matrix.org for packages

See https://github.com/vector-im/riot-web/issues/9497 (applies to more than just Olm)

* changelog

Using systemd-python allows for logging to the systemd journal,
as is documented in: `synapse/contrib/systemd/log_config.yaml`.

Signed-off-by: Silke Hofstra <silke@slxh.eu>

Move some rest endpoints to client reader

Fix schema upgrade when dropping tables

Avoid sending syntax errors from the manhole to sentry.

Add time-based account expiration

We need to drop tables in the correct order due to foreign table
constraints (on `application_services`), otherwise the DROP TABLE
command will fail.

Introduced in #4992.

Rewrite Datastore.get_server_verify_keys

Rewrite this so that it doesn't hammer the database.