Related to #223 (Github Pull Request)

Looks like these client ids are actually integers,
but unless we pass them as a string, the bridge would complain with
an error like:

    {"field":"data.auth.clientID","message":"is the wrong type","value":123456789012345678,"type":"string","schemaPath":["properties","auth","properties","clientID"]}

Explicitly-casting to a string should fix the problem.

The Discord bridge should probably be improved to handle both ints and
strings though.

Regression since 174a6fcd1b3, #204 (Github Pull Request),
which only affects new servers.

Old servers which had their passkey.pem file relocated were okay.

ef5e4ad061 intentionally makes us conform to
the logging format suggested by the official Docker image.

Reverting this part, because it's uglier.

This likely should be fixed upstream as well though.

Somewhat related to #213 (Github Pull Request).

We've been moving in the opposite direction for quite a long time.
All services should just leave logging to systemd's journald.

Fixes a regression introduced during the upgrade to
Synapse v1.1.0 (in 2b3865ceea).

Since Synapse v1.1.0 upgraded to Python 3.7
(https://github.com/matrix-org/synapse/pull/5546),
we need to use a different modules directory when mounting
password provider modules.

Fixes a problem introduced by da6edc9cba.

Related to #145 (Github Pull Request).

This is a new feature of Synapse v1.1.0.

Discussed in #145 (Github Pull Request).

Well, `config.yaml` has been playbook-managed for a long time.
It's now extended to match the default sample config of the Discord
bridge.

With this patch, we also make `registration.yaml` playbook-managed,
which leads us to consistency with all other bridges.

Along with that, we introduce `./config` and `./data` separation,
like we do for the other bridges.

I've been thinking of doing before, but haven't.

Now that the Whatsapp bridge does it (since 4797469383),
it makes sense to do it for all other bridges as well.
(Except for the IRC bridge - that one manages most of registration.yaml by itself)

Doesn't matter much, but it makes it consistent with the other bridges.

- following spantaleev transition of the telegram brigde
- adding a validate_config task

appservice-irc doesn't have permission to create files in its project
directory and the intention is to log to the console, anyway. By
commenting out the file names, appservice-irc won't attempt to open the
files.

This means we need to explicitly specify a `media_url` now,
because without it, `url` would be used for building public URLs to
files/images. That doesn't work when `url` is not a public URL.

Regression since 4e8543ce21

Until now, if `--tags=setup-synapse` was used, bridge tasks would not
run and bridges would fail to register with the `matrix-synapse` role.
This means that Synapse's configuration would be generated with an empty
list of appservices (`app_service_config_files: []`).

.. and then bridges would fail, because Synapse would not be aware of
there being any bridges.

From now on, bridges always run their init tasks and always register
with Synapse.

For the Telegram bridge, the same applies to registering with
matrix-nginx-proxy. Previously, running `--tags=setup-nginx-proxy` would
get rid of the Telegram endpoint configuration for the same reason.
Not anymore.

Note: https://www.us-cert.gov/ncas/current-activity/2019/06/13/Exim-Releases-Security-Patches

That said, I don't believe we've been affected.
Not in a bad way at least, because:
- we run exim as non-root and capabilities dropped
- we run exim in a private Docker network with known trusted relayers
(Synapse and mxisd)

I've not found this welcome bot to work at all in my previous attempts.
It would simply not reply, even though federation works.

It seems like this is also a potential privacy issue, as per
https://gist.github.com/maxidorius/5736fd09c9194b7a6dc03b6b8d7220d0

With most people on Synapse v0.99+ and Synapse v1.0 now available,
we should no longer try to be backward compatible with Synapse 0.34,
because this just complicates the instructions for no good reason.

Using `|to_json` on a string is expected to correctly wrap it in quotes (e.g. `"4"`).
Wrapping it explicitly in double-quotes results in undesirable double-quoting (`""4""`).