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.

Related to:

- c203bef912
- https://github.com/Awesome-Technologies/synapse-admin/issues/468

0.9.x is broken: https://github.com/Awesome-Technologies/synapse-admin/issues/468

A fix for this major regression got merged 2 hours after 0.9.1 was tagged,
but one week later there's still no 0.9.2. Shame.

`always` is an nginx suffix, which shouldn't have been added to these.

This may proof useful to someone in the future.

We've had it on `matrix-nginx-proxy` before, but
our initial support for Traefik did not include any of these security
headers.

Previously, we had to run it at a subpath, like `/synapse-admin`.

We can now dedicate a whole domain and the `/` path to it, should we
wish to do so.

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now.

Related to 6a31fba346d9da434, 6a31fba346.

Related to https://github.com/Awesome-Technologies/synapse-admin/issues/322

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.