Fixup for b88b6ae7a3

`matrix_container_global_registry_prefix_override` may look similar to
the old `matrix_container_global_registry_prefix` variable
(removed in d6bf789710), but it's different.

The old `matrix_container_global_registry_prefix` variable was just a hardcode of `docker.io/` and roles that
needed to refer to `docker.io/` could use it. However, this was:

- not used by all roles, because some need another registry (not `docker.io/`)
- used only by roles within the playbook (`roles/custom`), not external roles

Overriding the old `matrix_container_global_registry_prefix` variable was rather pointless,
as it didn't cover everything.

The new `matrix_container_global_registry_prefix_override` variable, on the other hand,
lets you override the registry prefix for all components, regardless of whether they
use `docker.io/` or another registry by default.

This is useful to people who have somehow mirrored all container images to their own registry,
as it provides them with a single variable they can flip to influence the whole playbook.

This:

- brings consistency - no more mixing `_name_prefix` and `_registry_prefix`
- adds extensibility - a future patch will allow reconfiguring all registry prefixes for all roles in the playbook

We still have `_docker_` vs `_container_` inconsistencies.
These may be worked on later.

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

Update docs/maintenance-postgres.md: add a copyright header

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

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

Update docs for Ansible

This commit changes ansible.md title and adds a link to the page on docs/README.md to improve discoverability of the guide a little bit.

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

Update ajbura/cinny Docker tag to v4.4.0

Update docs related to installation: minor edits

- Reduce width of the table for DNS configuration

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

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

Partially reverts ac26cc1cb0.

The configurability introduced there is still available, so people can
easily disable this, if necessary.

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

This is done for a few reasons:

- less globals and more indepdendence for each role is better. We rely
  on various externally-hosted roles and they don't rely on this global
  either.

- `matrix_container_global_registry_prefix` could make people think they
  could just override this variable and have all their images pull from
  elsewhere. This is rarely the case, unless you've taken special care
  to mirror all the various components (from their respective
  registries) to your own. In such a case, you probably know what you're
  mirroring and can adjust individual variables.

- nowadays, various components live on different registries.
  With Docker Inc tightening rate limits for Docker Hub, it's even more
  likely that we'll see increased diversity in where images are hosted

Update docs: add copyright headers

Add license information to files for MX bridges

Those authors were picked up based on the current status (dae0f44603), the others (around 30 people whose contributions have been removed) being grouped as "MDAD project contributors".

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

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

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

As the future for the MX bridges in this playbook and by themselves seems uncertain, this commit adds license information in SPDX format to the files for those bridges, before the bridges would be deprecated and possibly get removed from the project.

Please note that .license files are added for the files which would be broken if such information are added as header, following the REUSE's specification.

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

`-t` works on both old and new Docker versions, so it's best to use that.