synapse: Add support for appservices and use secrets better

roles/synapse/templates/doublepuppet-registration.yaml.j2

@@ -0,0 +1,15 @@
+---
+# vim:ft=yaml
+# {{ ansible_managed }}
+
+id: doublepuppet
+url:
+as_token: "{{ synapse_doublepuppet_token }}"
+hs_token: doublepuppethstoken
+sender_localpart: doublepuppetsenderlocalpart
+rate_limited: false
+
+namespaces:
+  users:
+    - regex: '@.*:{{ synapse_server_name | replace(".", "\.") }}'
+      exclusive: false