synapse: Use matrix authentication service

roles/synapse/meta/argument_specs.yaml

@@ -17,6 +17,14 @@ argument_specs:
           - This is used to set the public_baseurl option for synapse (with https:// and trailing / added)
         type: str
         required: true
+      synapse_mas_secrets:
+        description: Passed to the matrix_authentication_service role
+        type: dict
+        required: true
+      synapse_mas_domain:
+        description: The public-facing domain that clients use to access matrix authentication service. Defaults to auth.`synapse_external_domain`
+        type: str
+        required: false
       synapse_signing_key:
         description: The homeserver signing key
         type: str