This commit adopts the common format which can be seen for BorgBackup. It should be probably helpful, though I am not quite sure how much.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update roles/custom/matrix-coturn/defaults/main.yml: edit an instruction for creating a strong password

Follow-up to 6b87d1aa7d

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update examples/vars.yml: add a whitespace character for indenting

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

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Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update docs/configuring-playbook-turn.md: add a section for description about installing

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update docs/configuring-playbook-turn.md and a related file

- Edit the introducion based on docs/configuring-playbook-client-element-web.md
- Adopt the commont format by creating the section "Adjusting the playbook configuration"
- Add the section "Extending the configuration"
- Move the section "Disabling Coturn" to the bottom

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Fix capitalization: Coturn → coturn

See: https://github.com/coturn/coturn. Note that "coturn" is not capitalized even on the start of a sentence, except some rare cases like on the releases page: https://github.com/coturn/coturn/releases

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

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Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Add a global config option for Docker network MTU

* Upgrade systemd_docker_base (v1.2.0-0 -> v1.3.0-0)

The new version includes `devture_systemd_docker_base_container_networks_driver_options`
due to 3cc7d12396

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3502

* Switch from passing matrix_playbook_docker_network_mtu to respecting devture_systemd_docker_base_container_networks_driver_options

Related to:
- 3cc7d12396
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3502

* Update all roles to versions that respect `devture_systemd_docker_base_container_networks_driver_options`

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Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Related to 0241c71a4c

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3270#issuecomment-2143782962

With this change, it should be possible for people to adjust the Docker
dependency from `docker.service` to something else (e.g. `pkg-ContainerManager-dockerd.service`),
or to completely eliminate it by setting `devture_systemd_docker_base_docker_service_name` to an empty string.

This makes it easier for people to use the playbook against a Synology DSM server.

All homeserver implementations have been updated to support this as
well.

It's just Jitsi that possibly doesn't work with anything other than `auth-secret`.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3191

Not that it seems necessary right now, but it makes it consistent with
all other roles.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2592

.. and try to auto-switch between `bind` and `volume` depending on
whether there's a slash in the `src` path.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2482

This helps large deployments which need to open up thousands of ports
(matrix_coturn_turn_udp_min_port, matrix_coturn_turn_udp_min_port)

On a test VM, opening 1k ports takes 17 seconds for Docker to "publish"
all of these ports (setting up forwarding rules with the firewall, etc),
so service startup and shutdown take a long amount of time.

If host-networking is used, there's no need to open any ports at all
and startup/shutdown can be quick.

Inspired by: https://www.rtcsec.com/article/cve-2020-26262-bypass-of-coturns-access-control-protection/

Part of a security hardening provoked by:
https://www.rtcsec.com/article/cve-2020-26262-bypass-of-coturns-access-control-protection/

- forego removing Docker images - it's not effective anyway, because it
  only removes the last version.. which is a drop in the bucket, usually

- do not reload systemd - it's none of our business. `--tags=start`,
  etc., handle this

- combine all uninstall tasks under a single block, which only runs if
  we detect traces (a leftover systemd .service file) of the component.
  If no such .service is detected, we skip them all. This may lead to
  incorect cleanup in rare cases, but is good enough for the most part.

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.