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-bridge-appservice-slack/templates/config.yaml.j2

@@ -0,0 +1,35 @@
+#jinja2: lstrip_blocks: True
+slack_hook_port: {{ matrix_appservice_slack_slack_port }}
+inbound_uri_prefix: "{{ matrix_appservice_slack_inbound_uri_prefix }}"
+bot_username: "{{ matrix_appservice_slack_bot_name }}"
+username_prefix: {{ matrix_appservice_slack_user_prefix }}
+
+homeserver:
+    server_name: "{{ matrix_domain }}"
+    url: "{{ matrix_appservice_slack_homeserver_url }}"
+    media_url: "{{ matrix_appservice_slack_homeserver_media_url }}"
+
+# Real Time Messaging API (RTM)
+# Optional if slack_hook_port and inbound_uri_prefix are defined, required otherwise.
+#
+rtm:
+  # Use the RTM API to listen for requests, which does not require
+  # the bridge to listen on the hook port.
+  # You should leave this enabled, unless you plan to use the
+  # bridge exclusively for webhooks.
+  #
+  enable: true
+
+  # Logging level specific to RTM traffic.
+  #
+  log_level: "silent"
+
+{% if matrix_appservice_slack_database_engine == 'nedb' %}
+dbdir: "/data"
+{% else %}
+db:
+    engine: {{ matrix_appservice_slack_database_engine|to_json }}
+    connectionString: {{ matrix_appservice_slack_database_connectionString|to_json }}
+{% endif %}
+
+matrix_admin_room: "{{ matrix_appservice_slack_control_room_id }}"

roles/custom/matrix-bridge-appservice-slack/templates/systemd/matrix-appservice-slack.service.j2

@@ -0,0 +1,45 @@
+#jinja2: lstrip_blocks: "True"
+[Unit]
+Description=Matrix Appservice Slack bridge
+{% for service in matrix_appservice_slack_systemd_required_services_list %}
+Requires={{ service }}
+After={{ service }}
+{% endfor %}
+{% for service in matrix_appservice_slack_systemd_wanted_services_list %}
+Wants={{ service }}
+{% endfor %}
+DefaultDependencies=no
+
+[Service]
+Type=simple
+Environment="HOME={{ matrix_systemd_unit_home_path }}"
+ExecStartPre=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} kill matrix-appservice-slack 2>/dev/null || true'
+ExecStartPre=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} rm matrix-appservice-slack 2>/dev/null || true'
+
+# Intentional delay, so that the homeserver (we likely depend on) can manage to start.
+ExecStartPre={{ matrix_host_command_sleep }} 5
+
+ExecStart={{ matrix_host_command_docker }} run --rm --name matrix-appservice-slack \
+			--log-driver=none \
+			--user={{ matrix_user_uid }}:{{ matrix_user_gid }} \
+			--cap-drop=ALL \
+			--network={{ matrix_docker_network }} \
+			{% if matrix_appservice_slack_container_http_host_bind_port %}
+			-p {{ matrix_appservice_slack_container_http_host_bind_port }}:{{matrix_appservice_slack_slack_port}} \
+			{% endif %}
+			-v {{ matrix_appservice_slack_config_path }}:/config:z \
+			-v {{ matrix_appservice_slack_data_path }}:/data:z \
+			{% for arg in matrix_appservice_slack_container_extra_arguments %}
+			{{ arg }} \
+			{% endfor %}
+			{{ matrix_appservice_slack_docker_image }} \
+			node app.js -p {{matrix_appservice_slack_matrix_port}} -c /config/config.yaml -f /config/slack-registration.yaml
+
+ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} kill matrix-appservice-slack 2>/dev/null || true'
+ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} rm matrix-appservice-slack 2>/dev/null || true'
+Restart=always
+RestartSec=30
+SyslogIdentifier=matrix-appservice-slack
+
+[Install]
+WantedBy=multi-user.target