This requires at least `v1.7.0-2` of the `prometheus-node-exporter`
Ansible role.

This is an attempt at optimizing service startup.

The effect is most pronounced when many services are restarted one by one.
The systemd service manager role sometimes does this - for example when `just install-service synapse` runs.
In such cases, a 5-second delay for each Synapse worker service
(or other bridge/bot service that waits on the homeserver) quickly adds up to a lot.

When services are all stopped fully and then started, the effect is not so pronounced, because
`matrix-synapse.service` starts first and pulls all worker services (defined as `Wants=` for it).
Later on, when the systemd service manager role "starts" these worker services, they're started already.
Even if they had a 5-second wait each, it would have happened in parallel.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3090

Related to https://github.com/mautrix/signal/issues/422

`--mount` is safer, as `-v` has the side-effect of creating the "source"
destination as a directory if it doesn't exist yet.
We don't need such magic.

Related to e5130372b9.

Depending on the `options` that people provide, this may break
compatibility.

Depending on the `options` that people provide, this may break
compatibility.

This is what we do for Synapse as well.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3088

Looks like the migration to the Go-based Signal bridge hardcoded the
`signalbot` username instead of using the variable we had.
Related to: https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3041

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3089

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3086

Such a core service probably belongs better when it's in the homeserver network

This is mostly so as to avoid referring to variables from other roles,
like `matrix_nginx_proxy_proxy_matrix_client_api_addr_with_container`.

This should come (and already does) from group_vars/matrix_servers