Make roles more independent of one another

With this change, the following roles are now only dependent
on the minimal `matrix-base` role:
- `matrix-corporal`
- `matrix-coturn`
- `matrix-mailer`
- `matrix-mxisd`
- `matrix-postgres`
- `matrix-riot-web`
- `matrix-synapse`

The `matrix-nginx-proxy` role still does too much and remains
dependent on the others.

Wiring up the various (now-independent) roles happens
via a glue variables file (`group_vars/matrix-servers`).
It's triggered for all hosts in the `matrix-servers` group.

According to Ansible's rules of priority, we have the following
chain of inclusion/overriding now:
- role defaults (mostly empty or good for independent usage)
- playbook glue variables (`group_vars/matrix-servers`)
- inventory host variables (`inventory/host_vars/matrix.<your-domain>`)

All roles default to enabling their main component
(e.g. `matrix_mxisd_enabled: true`, `matrix_riot_web_enabled: true`).
Reasoning: if a role is included in a playbook (especially separately,
in another playbook), it should "work" by default.

Our playbook disables some of those if they are not generally useful
(e.g. `matrix_corporal_enabled: false`).

roles/matrix-riot-web/defaults/main.yml

@@ -1,13 +1,17 @@
-# By default, this playbook installs the Riot.IM web UI on the `hostname_riot` domain.
-# If you wish to connect to your Matrix server by other means,
-# you may wish to disable this.
 matrix_riot_web_enabled: true
 
 matrix_riot_web_docker_image: "bubuntux/riot-web:v0.17.8"
 
 matrix_riot_web_data_path: "{{ matrix_base_data_path }}/riot-web"
 
+matrix_riot_web_container_expose_port: false
+
+# List of systemd services that matrix-riot-web.service depends on
+matrix_riot_web_systemd_required_services_list: ['docker.service']
+
 # Riot config.json customizations
+matrix_riot_web_default_hs_url: ""
+matrix_riot_web_default_is_url: ~
 matrix_riot_web_disable_custom_urls: true
 matrix_riot_web_disable_guests: true
 matrix_riot_web_integrations_ui_url: "https://scalar.vector.im/"
@@ -18,7 +22,6 @@ matrix_riot_web_integrations_jitsi_widget_url: "https://scalar.vector.im/api/wid
 matrix_riot_web_roomdir_servers: ['matrix.org']
 matrix_riot_web_welcome_user_id: "@riot-bot:matrix.org"
 
-
 # Riot home.html customizations
 # Default home.html template file
 matrix_riot_web_homepage_template: "{{ role_path }}/templates/home.html.j2"

roles/matrix-riot-web/tasks/main.yml

@@ -2,6 +2,12 @@
   tags:
     - always
 
+- import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: "run_setup and matrix_riot_web_enabled"
+  tags:
+    - setup-all
+    - setup-riot-web
+
 - import_tasks: "{{ role_path }}/tasks/setup_riot_web.yml"
   when: run_setup
   tags:

roles/matrix-riot-web/tasks/validate_config.yml

@@ -0,0 +1,9 @@
+---
+
+- name: Fail if required riot-web settings not defined
+  fail:
+    msg: >
+      You need to define a required configuration setting (`{{ item }}`) for using riot-web.
+  when: "vars[item] == ''"
+  with_items:
+    - "matrix_riot_web_default_hs_url"

roles/matrix-riot-web/templates/config.json.j2

@@ -1,13 +1,13 @@
 {
-    "default_hs_url": "{{ matrix_homeserver_url }}",
-    "default_is_url": "{{ matrix_identity_server_url }}",
-    "disable_custom_urls": {{ matrix_riot_web_disable_custom_urls|lower }},
-    "disable_guests": {{ matrix_riot_web_disable_guests|lower }},
+    "default_hs_url": {{ matrix_riot_web_default_hs_url|to_json }},
+    "default_is_url": {{ matrix_riot_web_default_is_url|to_json }},
+    "disable_custom_urls": {{ matrix_riot_web_disable_custom_urls|to_json }},
+    "disable_guests": {{ matrix_riot_web_disable_guests|to_json }},
     "brand": "Riot",
-    "integrations_ui_url": "{{ matrix_riot_web_integrations_ui_url }}",
-    "integrations_rest_url": "{{ matrix_riot_web_integrations_rest_url }}",
+    "integrations_ui_url": {{ matrix_riot_web_integrations_ui_url|to_json }},
+    "integrations_rest_url": {{ matrix_riot_web_integrations_rest_url|to_json }},
     "integrations_widgets_urls": {{ matrix_riot_web_integrations_widgets_urls|to_json }},
-    "integrations_jitsi_widget_url": "{{ matrix_riot_web_integrations_jitsi_widget_url }}",
+    "integrations_jitsi_widget_url": {{ matrix_riot_web_integrations_jitsi_widget_url|to_json }},
     "bug_report_endpoint_url": "https://riot.im/bugreports/submit",
     "enableLabs": true,
     "roomDirectory": {

roles/matrix-riot-web/templates/systemd/matrix-riot-web.service.j2

@@ -1,7 +1,9 @@
 [Unit]
-Description=Matrix Riot web server
-After=docker.service
-Requires=docker.service
+Description=Matrix riot-web server
+{% for service in matrix_riot_web_systemd_required_services_list %}
+Requires={{ service }}
+After={{ service }}
+{% endfor %}
 
 [Service]
 Type=simple
@@ -12,7 +14,7 @@ ExecStart=/usr/bin/docker run --rm --name matrix-riot-web \
 			-v {{ matrix_riot_web_data_path }}/config.json:/etc/riot-web/config.json:ro \
 			-v {{ matrix_riot_web_data_path }}/home.html:/etc/riot-web/home.html:ro \
 			--network={{ matrix_docker_network }} \
-			{% if not matrix_nginx_proxy_enabled %}
+			{% if matrix_riot_web_container_expose_port %}
 			-p 127.0.0.1:8765:80 \
 			{% endif %}
 			{{ matrix_riot_web_docker_image }}