Add matrix-rustpush-bridge (iMessage)

Add the matrix-rustpush-bridge role, a Matrix <-> iMessage bridge built
on the mautrix-go bridgev2 framework using RustPush (OpenBubbles backend).

Unlike the existing mautrix-imessage/wsproxy bridge, it talks directly to
Apple's push notification service, so it needs neither a running Mac nor a
wsproxy on the homeserver. Each user supplies a hardware key extracted from a
Mac through the bridge bot's login flow.

The bridge uses its own bot username and puppet namespace (rustpushbot,
rustpush_*) so it does not collide with the wsproxy iMessage bridge.

This bridge is in early development and may have stability issues.

roles/custom/matrix-bridge-rustpush/tasks/validate_config.yml

@@ -0,0 +1,20 @@
+# SPDX-FileCopyrightText: 2026 MDAD project contributors
+# SPDX-FileCopyrightText: 2026 Jason LaGuidice
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+---
+
+- name: Fail if required RustPush settings not defined
+  ansible.builtin.fail:
+    msg: >-
+      You need to define a required configuration setting (`{{ item.name }}`).
+  when: "item.when | bool and lookup('vars', item.name, default='') | string | length == 0"
+  with_items:
+    - {'name': 'matrix_rustpush_bridge_appservice_token', when: true}
+    - {'name': 'matrix_rustpush_bridge_homeserver_address', when: true}
+    - {'name': 'matrix_rustpush_bridge_homeserver_token', when: true}
+    - {'name': 'matrix_rustpush_bridge_database_hostname', when: "{{ matrix_rustpush_bridge_database_engine == 'postgres' }}"}
+    - {'name': 'matrix_rustpush_bridge_container_network', when: true}
+    - {'name': 'matrix_rustpush_bridge_metrics_proxying_hostname', when: "{{ matrix_rustpush_bridge_metrics_proxying_enabled }}"}
+    - {'name': 'matrix_rustpush_bridge_metrics_proxying_path_prefix', when: "{{ matrix_rustpush_bridge_metrics_proxying_enabled }}"}