Make Synapse use ma1sd (if enabled) for threepid registration

roles/matrix-synapse/defaults/main.yml

@@ -164,6 +164,14 @@ matrix_synapse_enable_group_creation: false
 # A list of 3PID types which users must supply when registering (possible values: email, msisdn).
 matrix_synapse_registrations_require_3pid: []
 
+# The server to use for email threepid validation. When empty, Synapse does it by itself.
+# Otherwise, this should be pointed to an identity server.
+matrix_synapse_account_threepid_delegates_email: ''
+
+# The server to use for phone number threepid validation. When empty, validation cannot happen, as Synapse doesn't support it.
+# To make it work, this should be pointed to an identity server.
+matrix_synapse_account_threepid_delegates_msisdn: ''
+
 # Users who register on this homeserver will automatically be joined to these rooms.
 # Rooms are to be specified using addresses (e.g. `#address:example.com`)
 matrix_synapse_auto_join_rooms: []