Related to 69f71f48

Discussed in https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/791

> WARNING: Error loading config file: .dockercfg: $HOME is not defined

.. which appeared in Docker 20.10.

Building `master` or something like this was failing.

Newer versions (`master`) use things like `--platform=...`,
which are not supported unless we enable the new BuildKit building
backend.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/756

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/737

I feel like timers are somewhat more complicated and dirty (compared to
cronjobs), but they come with these benefits:

- log output goes to journald
- on newer systemd distros, you can see when the timer fired, when it
will fire, etc.
- we don't need to rely on cron (reducing our dependencies to just
systemd + Docker)

Cronjobs work well, but it's one more dependency that needs to be
installed. We were even asking people to install it manually
(in `docs/prerequisites.md`), which could have gone unnoticed.

Once in a while someone says "my SSL certificates didn't renew"
and it's likely because they forgot to install a cron daemon.

Switching to systemd timers means that installation is simpler
and more unified.

We'll be adding `.timer` units later on, so it's good to be
more explicit.

This reverts commit 2a25b63bb6.

Looking at other roles, we trigger building regardless of this.
It's better to always trigger it, because it's less fragile.
If the build fails and we only trigger it on "git changes"
then we won't trigger it for a while. That's not good.

Triggering it each and every time may seem like a waste,
but it supposedly runs quickly due to Docker caching.

This variable has been useless since 2019-01-08.
We probably don't need to check for its usage anymore,
given how much time has passed since then, but ..

Selfbuild appservice-slack bridge

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/793

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/786

Local rebuild for Telegram

Before we potentially clone to that path, we'd better make sure it exists.

We also simplify `when` statements a bit.
Given that we're in `setup_install.yml`, we know that the bridge is enabled,
so there's no need to check for that.

This is a bit misleading, because the old Docker image
was tagged as `4.93.1`. There hasn't been a `4.93.1` version yet though.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/792

Related to d5945c6e78

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/778

Call API list tokens enpoint

Closes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/755

Not sure if it breaks with them or not, but no other directive
uses quotes and the nginx docs show examples without quotes,
so we're being consistent with all of that.

Code was clean up and simplified to make it simpler and easier to
maintain. No features were modified.

The different configurations are now all lower case, for consistent
naming.

`matrix_nginx_proxy_ssl_config` is now called
`matrix_nginx_proxy_ssl_preset`. The different options for "modern",
"intermediate" and "old" are stored in the main.yml file, instead of
being hardcoded in the configuration files. This will improve the
maintainability of the code.

The "custom" preset was removed. Now if one of the variables is set, it
will use it instead of the preset. This will allow to mix and match more
easily, for example using all the intermediate options but only
supporting TLSv1.2. This will also provide better backward
compatibility.

Fix appservice-slack default db: nedb