Add conditional restart support to service roles

Track config/image/systemd changes via register: directives and compute
a _restart_necessary variable for each service role, allowing the
systemd_service_manager to skip unnecessary restarts during install-* runs.

Covers 22 service roles: alertmanager-receiver, appservice-draupnir-for-all,
bridge-mautrix-wsproxy (+ syncproxy), cactus-comments, cactus-comments-client,
corporal, element-admin, ldap-registration-proxy, livekit-jwt-service, matrixto,
pantalaimon, prometheus-nginxlog-exporter, rageshake, registration, static-files,
sygnal, synapse-admin, synapse-auto-compressor, synapse-reverse-proxy-companion,
synapse-usage-exporter, and user-verification-service.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

roles/custom/matrix-registration/defaults/main.yml

@@ -167,3 +167,13 @@ matrix_registration_configuration_extension: "{{ matrix_registration_configurati
 # Holds the final matrix-registration configuration (a combination of the default and its extension).
 # You most likely don't need to touch this variable. Instead, see `matrix_registration_configuration_yaml`.
 matrix_registration_configuration: "{{ matrix_registration_configuration_yaml | from_yaml | combine(matrix_registration_configuration_extension, recursive=True) }}"
+
+# matrix_registration_restart_necessary controls whether the service
+# will be restarted (when true) or merely started (when false) by the
+# systemd service manager role (when conditional restart is enabled).
+#
+# This value is automatically computed during installation based on whether
+# any configuration files, the systemd service file, or the container image changed.
+# The default of `false` means "no restart needed" — appropriate when the role's
+# installation tasks haven't run (e.g., due to --tags skipping them).
+matrix_registration_restart_necessary: false

roles/custom/matrix-registration/tasks/setup_install.yml

@@ -63,10 +63,10 @@
     force_source: "{{ matrix_registration_docker_image_force_pull if ansible_version.major > 2 or ansible_version.minor >= 8 else omit }}"
     force: "{{ omit if ansible_version.major > 2 or ansible_version.minor >= 8 else matrix_registration_docker_image_force_pull }}"
   when: "not matrix_registration_container_image_self_build | bool"
-  register: result
+  register: matrix_registration_container_image_pull_result
   retries: "{{ devture_playbook_help_container_retries_count }}"
   delay: "{{ devture_playbook_help_container_retries_delay }}"
-  until: result is not failed
+  until: matrix_registration_container_image_pull_result is not failed
 
 - name: Ensure matrix-registration repository is present when self-building
   ansible.builtin.git:
@@ -106,6 +106,7 @@
     mode: 0644
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_registration_config_result
 
 - name: Ensure matrix-registration support files installed
   ansible.builtin.template:
@@ -116,6 +117,7 @@
     group: "{{ matrix_group_name }}"
   with_items:
     - labels
+  register: matrix_registration_support_files_result
 
 - name: Ensure matrix-registration container network is created
   community.general.docker_network:
@@ -129,6 +131,18 @@
     src: "{{ role_path }}/templates/systemd/matrix-registration.service.j2"
     dest: "{{ devture_systemd_docker_base_systemd_path }}/matrix-registration.service"
     mode: 0644
+  register: matrix_registration_systemd_service_result
+
+- name: Determine whether matrix-registration needs a restart
+  ansible.builtin.set_fact:
+    matrix_registration_restart_necessary: >-
+      {{
+        matrix_registration_migration_requires_restart | default(false)
+        or matrix_registration_config_result.changed | default(false)
+        or matrix_registration_support_files_result.changed | default(false)
+        or matrix_registration_systemd_service_result.changed | default(false)
+        or matrix_registration_container_image_pull_result.changed | default(false)
+      }}
 
 - name: Ensure matrix-registration.service restarted, if necessary
   ansible.builtin.service: