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.

* Auto trust new signal identities

from signald doku: when a remote key changes, set trust level to TRUSTED_UNVERIFIED instead of UNTRUSTED 
I find it much more convenient when new identities are automatically recognized as trusted, as the process to do that manually is cumbersome.
Should this the default behavior, or should i add an option to configure this behavior?

* Added option to trust new signal identities

* Using env file

* Renamed variable

* Corrected typo

* Use fully-qualified Ansible module name

* removed option trust_new_keys

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