This was an upstream documentation mistake that propagated to us
during the update in 25e7cac28d.

The upstream fix is here:

- 8f7f4d1dd1
- https://github.com/metio/matrix-alertmanager-receiver/pull/99

Ref:

- https://github.com/metio/matrix-alertmanager-receiver/releases/tag/2025.9.17
- https://github.com/metio/matrix-alertmanager-receiver/pull/94

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

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>

!aaabaa is used as an example of a room ID on https://spec.matrix.org/v1.12/#room-aliases

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

!qporfwt is used as an example of a room ID on https://spec.matrix.org/v1.12/#room-structure

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>

Supersedes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3539

Related to https://github.com/metio/matrix-alertmanager-receiver/pull/42

My alerts seem to contain `annotations.alertname` in the payload, so the
default configuration (coming from the matrix-alertmanager-receiver README)
seems to be outdated or something.