Add a variable to control Dendrite's disable_federation setting

roles/matrix-dendrite/defaults/main.yml

@@ -114,6 +114,10 @@ matrix_dendrite_trusted_id_servers:
   - "matrix.org"
   - "vector.im"
 
+# Controls whether Dendrite will federate at all.
+# Disable this to completely isolate your server from the rest of the Matrix network.
+matrix_dendrite_disable_federation: false
+
 # Default Dendrite configuration template which covers the generic use case.
 # You can customize it by controlling the various variables inside it.
 #