Move roles/matrix* to roles/custom/matrix*

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.

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

@@ -0,0 +1,68 @@
+---
+
+- ansible.builtin.set_fact:
+    matrix_systemd_services_list: "{{ matrix_systemd_services_list + ['matrix-cactus-comments.service'] }}"
+  when: matrix_cactus_comments_enabled | bool
+
+# If the matrix-synapse role is not used, these variables may not exist.
+- ansible.builtin.set_fact:
+    matrix_homeserver_container_runtime_injected_arguments: >
+      {{
+        matrix_homeserver_container_runtime_injected_arguments | default([])
+        +
+        ["--mount type=bind,src={{ matrix_cactus_comments_app_service_config_file }},dst=/matrix-cactus-comments.yaml,ro"]
+      }}
+
+    matrix_homeserver_app_service_runtime_injected_config_files: >
+      {{
+        matrix_homeserver_app_service_runtime_injected_config_files | default([])
+        +
+        ["/matrix-cactus-comments.yaml"]
+      }}
+  when: matrix_cactus_comments_enabled | bool
+
+- when: matrix_cactus_comments_enabled | bool and matrix_cactus_comments_serve_client_enabled | bool
+  tags:
+    - always
+  block:
+    - name: Fail if matrix-nginx-proxy role already executed
+      ansible.builtin.fail:
+        msg: >-
+          Trying to append Cactus Comment's reverse-proxying configuration to matrix-nginx-proxy,
+          but it's pointless since the matrix-nginx-proxy role had already executed.
+          To fix this, please change the order of roles in your playbook,
+          so that the matrix-nginx-proxy role would run after the matrix-cactus-comments role.
+      when: matrix_nginx_proxy_role_executed | default(False) | bool
+
+    - name: Mount volume
+      ansible.builtin.set_fact:
+        matrix_nginx_proxy_container_additional_volumes: >
+          {{
+            matrix_nginx_proxy_container_additional_volumes | default([])
+            +
+            [{"src": "{{ matrix_cactus_comments_client_path }}", "dst": "/cactus-comments/cactus-comments", "options": "ro"}]
+          }}
+
+    - name: Generate Cactus Comment proxying configuration for matrix-nginx-proxy
+      ansible.builtin.set_fact:
+        matrix_cactus_comments_nginx_proxy_configuration: |
+          location {{ matrix_cactus_comments_client_endpoint }} {
+              root {{ matrix_cactus_comments_client_nginx_path }};
+          }
+
+    - name: Register Cactus Comment proxying configuration with matrix-nginx-proxy
+      ansible.builtin.set_fact:
+        matrix_nginx_proxy_proxy_matrix_additional_server_configuration_blocks: |
+          {{
+            matrix_nginx_proxy_proxy_matrix_additional_server_configuration_blocks | default([])
+            +
+            [matrix_cactus_comments_nginx_proxy_configuration]
+          }}
+
+    - name: Warn about reverse-proxying if matrix-nginx-proxy not used
+      ansible.builtin.debug:
+        msg: >-
+          NOTE: You've enabled Cactus Comments but are not using the matrix-nginx-proxy
+          reverse proxy.
+          Please make sure that you're proxying client files in {{ matrix_cactus_comments_client_path }} correctly
+      when: "not matrix_nginx_proxy_enabled | default(False) | bool"