Move roles/matrix* to roles/custom/matrix*

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.

roles/custom/matrix-registration/templates/config.yaml.j2

@@ -0,0 +1,31 @@
+server_location: {{ matrix_registration_server_location|to_json }}
+server_name: {{ matrix_registration_server_name|to_json }}
+shared_secret: {{ matrix_registration_shared_secret|to_json }}
+admin_secret: {{ matrix_registration_admin_secret|to_json }}
+riot_instance: {{ matrix_registration_riot_instance|to_json }}
+db: {{ matrix_registration_db|to_json }}
+host: '0.0.0.0'
+port: 5000
+rate_limit: ["100 per day", "10 per minute"]
+allow_cors: false
+logging:
+  disable_existing_loggers: False
+  version: 1
+  root:
+    level: DEBUG
+    handlers: [console]
+  formatters:
+    brief:
+      format: '%(name)s - %(levelname)s - %(message)s'
+    precise:
+      format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
+  handlers:
+    console:
+      class: logging.StreamHandler
+      level: INFO
+      formatter: brief
+      stream: ext://sys.stdout
+# password requirements
+password:
+  min_length: 8
+base_url: {{ matrix_registration_base_url|to_json }}