Add appservice-double-puppet double-puppeting support to mautrix-discord

Shared Secret Auth double puppeting still works for this bridge, but
is deprecated and will go away in the future.

roles/custom/matrix-bridge-mautrix-discord/defaults/main.yml

@@ -100,10 +100,9 @@ matrix_mautrix_discord_appservice_database_uri: "{{
 	}[matrix_mautrix_discord_database_engine]
 }}"
 
-# Can be set to enable automatic double-puppeting via Shared Secret Auth (https://github.com/devture/matrix-synapse-shared-secret-auth).
-matrix_mautrix_discord_login_shared_secret: ''
-matrix_mautrix_discord_bridge_login_shared_secret_map:
-  "{{ {matrix_mautrix_discord_homeserver_domain: matrix_mautrix_discord_login_shared_secret} if matrix_mautrix_discord_login_shared_secret else {} }}"
+matrix_mautrix_discord_bridge_login_shared_secret_map: "{{ matrix_mautrix_discord_bridge_login_shared_secret_map_auto | combine(matrix_mautrix_discord_bridge_login_shared_secret_map_custom) }}"
+matrix_mautrix_discord_bridge_login_shared_secret_map_auto: {}
+matrix_mautrix_discord_bridge_login_shared_secret_map_custom: {}
 
 # Servers to always allow double puppeting from
 matrix_mautrix_discord_bridge_double_puppet_server_map:

roles/custom/matrix-bridge-mautrix-discord/tasks/validate_config.yml

@@ -12,3 +12,12 @@
     - {'name': 'matrix_mautrix_discord_homeserver_public_address', when: true}
     - {'name': 'matrix_mautrix_discord_container_network', when: true}
     - {'name': 'matrix_mautrix_discord_database_hostname', when: "{{ matrix_mautrix_discord_database_engine == 'postgres' }}"}
+
+- name: (Deprecation) Catch and report renamed settings
+  ansible.builtin.fail:
+    msg: >-
+      Your configuration contains a variable, which now has a different name.
+      Please change your configuration to rename the variable (`{{ item.old }}` -> `{{ item.new }}`).
+  when: "item.old in vars"
+  with_items:
+    - {'old': 'matrix_mautrix_discord_login_shared_secret', 'new': '<removed>'}