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-mxisd/tasks/main.yml

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

roles/matrix-mxisd/tasks/setup_mxisd.yml

@@ -4,49 +4,6 @@
 # Tasks related to setting up mxisd
 #
 
-- name: (Deprecation) Warn about mxisd variables that are not used anymore
-  fail:
-    msg: >
-      The `{{ item }}` variable defined in your configuration is not used by this playbook anymore!
-      You'll need to adapt to the new way of extending mxisd configuration.
-      See the CHANGELOG and the `matrix_mxisd_configuration_extension_yaml` variable for more information and examples.
-  when: "matrix_mxisd_enabled and item in vars"
-  with_items:
-    - 'matrix_mxisd_ldap_enabled'
-    - 'matrix_mxisd_ldap_connection_host'
-    - 'matrix_mxisd_ldap_connection_tls'
-    - 'matrix_mxisd_ldap_connection_port'
-    - 'matrix_mxisd_ldap_connection_baseDn'
-    - 'matrix_mxisd_ldap_connection_baseDns'
-    - 'matrix_mxisd_ldap_connection_bindDn'
-    - 'matrix_mxisd_ldap_connection_bindPassword'
-    - 'matrix_mxisd_ldap_filter'
-    - 'matrix_mxisd_ldap_attribute_uid_type'
-    - 'matrix_mxisd_ldap_attribute_uid_value'
-    - 'matrix_mxisd_ldap_connection_bindPassword'
-    - 'matrix_mxisd_ldap_attribute_name'
-    - 'matrix_mxisd_ldap_attribute_threepid_email'
-    - 'matrix_mxisd_ldap_attribute_threepid_msisdn'
-    - 'matrix_mxisd_ldap_identity_filter'
-    - 'matrix_mxisd_ldap_identity_medium'
-    - 'matrix_mxisd_ldap_auth_filter'
-    - 'matrix_mxisd_ldap_directory_filter'
-    - 'matrix_mxisd_template_config'
-
-- name: Ensure mxisd configuration does not contain any dot-notation keys
-  fail:
-    msg: >
-      Since version 1.3.0, mxisd will not accept property-style configuration keys.
-      You have defined a key (`{{ item.key }}`) which contains a dot.
-      Instead, use nesting. See: https://github.com/kamax-matrix/mxisd/wiki/Upgrade#v130
-  when: "matrix_mxisd_enabled and '.' in item.key"
-  with_dict: "{{ matrix_mxisd_configuration }}"
-
-- name: Fail if mailer is not enabled
-  fail:
-    msg: "You need to enable the mailer service (`matrix_mailer_enabled`) to install mxisd"
-  when: "matrix_mxisd_enabled and not matrix_mailer_enabled"
-
 - name: Ensure mxisd paths exist
   file:
     path: "{{ item }}"

roles/matrix-mxisd/tasks/validate_config.yml

@@ -0,0 +1,47 @@
+---
+
+- name: (Deprecation) Warn about mxisd variables that are not used anymore
+  fail:
+    msg: >
+      The `{{ item }}` variable defined in your configuration is not used by this playbook anymore!
+      You'll need to adapt to the new way of extending mxisd configuration.
+      See the CHANGELOG and the `matrix_mxisd_configuration_extension_yaml` variable for more information and examples.
+  when: "item in vars"
+  with_items:
+    - 'matrix_mxisd_ldap_enabled'
+    - 'matrix_mxisd_ldap_connection_host'
+    - 'matrix_mxisd_ldap_connection_tls'
+    - 'matrix_mxisd_ldap_connection_port'
+    - 'matrix_mxisd_ldap_connection_baseDn'
+    - 'matrix_mxisd_ldap_connection_baseDns'
+    - 'matrix_mxisd_ldap_connection_bindDn'
+    - 'matrix_mxisd_ldap_connection_bindPassword'
+    - 'matrix_mxisd_ldap_filter'
+    - 'matrix_mxisd_ldap_attribute_uid_type'
+    - 'matrix_mxisd_ldap_attribute_uid_value'
+    - 'matrix_mxisd_ldap_connection_bindPassword'
+    - 'matrix_mxisd_ldap_attribute_name'
+    - 'matrix_mxisd_ldap_attribute_threepid_email'
+    - 'matrix_mxisd_ldap_attribute_threepid_msisdn'
+    - 'matrix_mxisd_ldap_identity_filter'
+    - 'matrix_mxisd_ldap_identity_medium'
+    - 'matrix_mxisd_ldap_auth_filter'
+    - 'matrix_mxisd_ldap_directory_filter'
+    - 'matrix_mxisd_template_config'
+
+- name: Ensure mxisd configuration does not contain any dot-notation keys
+  fail:
+    msg: >
+      Since version 1.3.0, mxisd will not accept property-style configuration keys.
+      You have defined a key (`{{ item.key }}`) which contains a dot.
+      Instead, use nesting. See: https://github.com/kamax-matrix/mxisd/wiki/Upgrade#v130
+  when: "'.' in item.key"
+  with_dict: "{{ matrix_mxisd_configuration }}"
+
+- name: Fail if required mxisd settings not defined
+  fail:
+    msg: >
+      You need to define a required configuration setting (`{{ item }}`) for using mxisd.
+  when: "vars[item] == ''"
+  with_items:
+    - "matrix_mxid_threepid_medium_email_connectors_smtp_host"