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-cactus-comments/defaults/main.yml

@@ -56,3 +56,13 @@ matrix_cactus_comments_systemd_required_services_list: "{{ [devture_systemd_dock
 matrix_cactus_comments_systemd_wanted_services_list: []
 
 matrix_cactus_comments_environment_variables_extension: ''
+
+# matrix_cactus_comments_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_cactus_comments_restart_necessary: false

roles/custom/matrix-cactus-comments/tasks/setup_install.yml

@@ -26,6 +26,7 @@
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
     mode: 0640
+  register: matrix_cactus_comments_config_env_result
 
 - name: Ensure matrix-cactus-comments appservice file created
   ansible.builtin.template:
@@ -34,6 +35,7 @@
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
     mode: 0640
+  register: matrix_cactus_comments_config_appservice_result
 
 - name: Ensure matrix-cactus-comments image is pulled
   community.docker.docker_image:
@@ -42,10 +44,10 @@
     force_source: "{{ matrix_cactus_comments_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_cactus_comments_docker_image_force_pull }}"
   when: "not matrix_cactus_comments_container_image_self_build | bool"
-  register: result
+  register: matrix_cactus_comments_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_cactus_comments_container_image_pull_result is not failed
 
 - name: Ensure matrix-cactus-comments repository is present on self-build
   ansible.builtin.git:
@@ -75,3 +77,14 @@
     src: "{{ role_path }}/templates/systemd/matrix-cactus-comments.service.j2"
     dest: "{{ devture_systemd_docker_base_systemd_path }}/matrix-cactus-comments.service"
     mode: 0644
+  register: matrix_cactus_comments_systemd_service_result
+
+- name: Determine whether matrix-cactus-comments needs a restart
+  ansible.builtin.set_fact:
+    matrix_cactus_comments_restart_necessary: >-
+      {{
+        matrix_cactus_comments_config_env_result.changed | default(false)
+        or matrix_cactus_comments_config_appservice_result.changed | default(false)
+        or matrix_cactus_comments_systemd_service_result.changed | default(false)
+        or matrix_cactus_comments_container_image_pull_result.changed | default(false)
+      }}