Send users a server notice about consent

When a user first syncs, we will send them a server notice asking them to
consent to the privacy policy if they have not already done so.

synapse/server_notices/server_notices_sender.py

@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from synapse.server_notices.consent_server_notices import ConsentServerNotices
+
+
+class ServerNoticesSender(object):
+    """A centralised place which sends server notices automatically when
+    Certain Events take place
+    """
+    def __init__(self, hs):
+        """
+
+        Args:
+            hs (synapse.server.HomeServer):
+        """
+        # todo: it would be nice to make this more dynamic
+        self._consent_server_notices = ConsentServerNotices(hs)
+
+    def on_user_syncing(self, user_id):
+        """Called when the user performs a sync operation.
+
+        This is only called when /sync (or /events) is called on the synapse
+        master. In a deployment with synchrotrons, on_user_ip is called
+
+        Args:
+            user_id (str): mxid of user who synced
+
+        Returns:
+            Deferred
+        """
+        return self._consent_server_notices.maybe_send_server_notice_to_user(
+            user_id,
+        )
+
+    def on_user_ip(self, user_id):
+        """Called when a worker process saw a client request.
+
+        Args:
+            user_id (str): mxid
+
+        Returns:
+            Deferred
+        """
+        return self._consent_server_notices.maybe_send_server_notice_to_user(
+            user_id,
+        )