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""`).

We do use some `:latest` images by default for the following services:
- matrix-dimension
- Goofys (in the matrix-synapse role)
- matrix-bridge-appservice-irc
- matrix-bridge-appservice-discord
- matrix-bridge-mautrix-facebook
- matrix-bridge-mautrix-whatsapp

It's terribly unfortunate that those software projects don't release
anything other than `:latest`, but that's how it is for now.

Updating that software requires that users manually do `docker pull`
on the server. The playbook didn't force-repull images that it already
had.

With this patch, it starts doing so. Any image tagged `:latest` will be
force re-pulled by the playbook every time it's executed.

It should be noted that even though we ask the `docker_image` module to
force-pull, it only reports "changed" when it actually pulls something
new. This is nice, because it lets people know exactly when something
gets updated, as opposed to giving the indication that it's always
updating the images (even though it isn't).

Bridges start matrix-synapse.service as a dependency, but
Synapse is sometimes slow to start, while bridges are quick to
hit it and die (if unavailable).

They'll auto-restart later, but .. this still breaks `--tags=start`,
which doesn't wait long enough for such a restart to happen.

This attempts to slow down bridge startup enough to ensure Synapse
is up and no failures happen at all.

Attempt to fix #192 (Github Issue), potential regression since
70487061f4.

Serializing as JSON/YAML explicitly is much better than relying on
magic (well, Python serialization being valid YAML..).
It seems like Python may prefix strings with `u` sometimes (Python 3?),
which causes Python serialization to not be compatible with YAML.

This doesn't replace all usage of `-v`, but it's a start.

People sometimes troubleshoot by deleting files (especially bridge
config files). Restarting Synapse with a missing registration.yaml file
for a given bridge, causes the `-v
/something/registration.yaml:/something/registration.yaml:ro` option
to force-create `/something/registration.yaml` as a directory.

When a path that's provided to the `-v` option is missing, Docker
auto-creates that path as a directory.
This causes more breakage and confusion later on.

We'd rather fail, instead of magically creating directories.
Using `--mount`, instead of `-v` is the solution to this.

From Docker's documentation:

> When you use --mount with type=bind, the host-path must refer to an existing path on the host.
> The path will not be created for you and the service will fail with an error if the path does not exist.

Fixes #171 (Github Issue).

Reasoning is the same as for matrix-org/synapse#5023.

For us, the journal used to contain `docker` for all services, which
is not very helpful when looking at them all together (`journalctl -f`).

The goal is to move each bridge into its own separate role.
This commit starts off the work on this with 2 bridges:
- mautrix-telegram
- mautrix-whatsapp

Each bridge's role (including these 2) is meant to:

- depend only on the matrix-base role

- integrate nicely with the matrix-synapse role (if available)

- integrate nicely with the matrix-nginx-proxy role (if available and if
required). mautrix-telegram bridge benefits from integrating with
it.

- not break if matrix-synapse or matrix-nginx-proxy are not used at all

This has been provoked by #174 (Github Issue).

Use Jinja2 lstrip_blocks option in templates to ensure consistent
indentation in generated files.

This prevents Ansible from sometimes failing to decrypt vault variables

The code used to check for a `homeserver.yaml` file and generate
a configuration (+ key) only if such a configuration file didn't exist.

Certain rare cases (setting up with one server name and then
changing to another) lead to `homeserver.yaml` being there,
but a `matrix.DOMAIN.signing.key` file missing (because the domain
changed).
A new signing key file would never get generated, because `homeserver.yaml`'s
existence used to be (incorrectly) satisfactory for us.

From now on, we don't mix things up like that.
We don't care about `homeserver.yaml` anymore, but rather
about the actual signing key.

The rest of the configuration (`homeserver.yaml` and
`matrix.DOMAIN.log.config`) is rebuilt by us in any case, so whether
it exists or not is irrelevant and doesn't need checking.

- matrix_enable_room_list_search - Controls whether searching the public room list is enabled.
 - matrix_alias_creation_rules - Controls who's allowed to create aliases on this server.
 - matrix_room_list_publication_rules - Controls who can publish and which rooms can be published in the public room list.

`{% matrix_s3_media_store_custom_endpoint_enabled %}` should have
been `{% if matrix_s3_media_store_custom_endpoint_enabled %}` instead.

Related to #132 (Github Pull Request).

that's not how it works

This (should) check if custom endpoint is enabled.

Creates the configuration variable to toggle custom endpoint and the default custom endpoint.

In most cases, there's not really a need to touch the system
firewall, as Docker manages iptables by itself
(see https://docs.docker.com/network/iptables/).

All ports exposed by Docker containers are automatically whitelisted
in iptables and wired to the correct container.

This made installing firewalld and whitelisting ports pointless,
as far as this playbook's services are concerned.

People that wish to install firewalld (for other reasons), can do so
manually from now on.

This is inspired by and fixes #97 (Github Issue).