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-synapse/tasks/main.yml

@@ -2,6 +2,12 @@
   tags:
     - always
 
+- import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: run_setup
+  tags:
+    - setup-all
+    - setup-synapse
+
 - import_tasks: "{{ role_path }}/tasks/setup_synapse_entrypoint.yml"
   when: run_setup
   tags:

roles/matrix-synapse/tasks/self_check_client_api.yml

@@ -1,20 +1,17 @@
 ---
 
-- set_fact:
-    matrix_client_api_url_endpoint_public: "https://{{ hostname_matrix }}/_matrix/client/versions"
-
 - name: Check Matrix Client API
   uri:
-    url: "{{ matrix_client_api_url_endpoint_public }}"
+    url: "{{ matrix_synapse_client_api_url_endpoint_public }}"
     follow_redirects: false
-  register: result_matrix_client_api
+  register: result_matrix_synapse_client_api
   ignore_errors: true
 
 - name: Fail if Matrix Client API not working
   fail:
-    msg: "Failed checking Matrix Client API is up at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_client_api_url_endpoint_public }}`). Is Synapse running? Is port 443 open in your firewall? Full error: {{ result_matrix_client_api }}"
-  when: "result_matrix_client_api.failed or 'json' not in result_matrix_client_api"
+    msg: "Failed checking Matrix Client API is up at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_synapse_client_api_url_endpoint_public }}`). Is Synapse running? Is port 443 open in your firewall? Full error: {{ result_matrix_synapse_client_api }}"
+  when: "result_matrix_synapse_client_api.failed or 'json' not in result_matrix_synapse_client_api"
 
 - name: Report working Matrix Client API
   debug:
-    msg: "The Matrix Client API at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_client_api_url_endpoint_public }}`) is working"
+    msg: "The Matrix Client API at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_synapse_client_api_url_endpoint_public }}`) is working"

roles/matrix-synapse/tasks/self_check_federation_api.yml

@@ -1,21 +1,18 @@
 ---
 
-- set_fact:
-    matrix_federation_api_url_endpoint_public: "https://{{ hostname_matrix }}:8448/_matrix/federation/v1/version"
-
 - name: Check Matrix Federation API
   uri:
-    url: "{{ matrix_federation_api_url_endpoint_public }}"
+    url: "{{ matrix_synapse_federation_api_url_endpoint_public }}"
     follow_redirects: false
     validate_certs: false
-  register: result_matrix_federation_api
+  register: result_matrix_synapse_federation_api
   ignore_errors: true
 
 - name: Fail if Matrix Federation API not working
   fail:
-    msg: "Failed checking Matrix Federation API is up at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_federation_api_url_endpoint_public }}`). Is Synapse running? Is port 8448 open in your firewall? Full error: {{ result_matrix_federation_api }}"
-  when: "result_matrix_federation_api.failed or 'json' not in result_matrix_federation_api"
+    msg: "Failed checking Matrix Federation API is up at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_synapse_federation_api_url_endpoint_public }}`). Is Synapse running? Is port 8448 open in your firewall? Full error: {{ result_matrix_synapse_federation_api }}"
+  when: "result_matrix_synapse_federation_api.failed or 'json' not in result_matrix_synapse_federation_api"
 
 - name: Report working Matrix Federation API
   debug:
-    msg: "The Matrix Federation API at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_federation_api_url_endpoint_public }}`) is working"
+    msg: "The Matrix Federation API at `{{ hostname_matrix }}` (checked endpoint: `{{ matrix_synapse_federation_api_url_endpoint_public }}`) is working"

roles/matrix-synapse/tasks/validate_config.yml

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