Move Gmessages encryption.pickle_key to a variable

Closes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3538

See: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3538#issuecomment-2405780285

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

@@ -148,6 +148,8 @@ matrix_mautrix_gmessages_bridge_encryption_default: "{{ matrix_bridges_encryptio
 matrix_mautrix_gmessages_bridge_encryption_require: false
 matrix_mautrix_gmessages_bridge_encryption_appservice: false
 matrix_mautrix_gmessages_bridge_encryption_key_sharing_allow: "{{ matrix_mautrix_gmessages_bridge_encryption_allow }}"
+# For compatibility with the older Gmessages bridge, you may wish to set the pickle key to: "go.mau.fi/mautrix-gmessages"
+matrix_mautrix_gmessages_bridge_encryption_pickle_key: mautrix.bridge.e2ee
 
 matrix_mautrix_gmessages_network_displayname_template: "{% raw %}{{or .FullName .PhoneNumber}}{% endraw %}"
 matrix_mautrix_gmessages_appservice_username_template: "{% raw %}gmessages_{{.}}{% endraw %}"

roles/custom/matrix-bridge-mautrix-gmessages/templates/config.yaml.j2

@@ -359,7 +359,7 @@ encryption:
     allow_key_sharing: {{ matrix_mautrix_gmessages_bridge_encryption_key_sharing_allow | to_json }}
     # Pickle key for encrypting encryption keys in the bridge database.
     # If set to generate, a random key will be generated.
-    pickle_key: mautrix.bridge.e2ee
+    pickle_key: {{ matrix_mautrix_gmessages_bridge_encryption_pickle_key | to_json }}
     # Options for deleting megolm sessions from the bridge.
     delete_keys:
         # Beeper-specific: delete outbound sessions when hungryserv confirms