Add better (jinja-based) messaging to the notifications and add some fixes for the email templates

data/model/legacy.py

@@ -579,6 +579,13 @@ def get_user(username):
     return None
 
 
+def get_namespace_user(username):
+  try:
+    return User.get(User.username == username)
+  except User.DoesNotExist:
+    return None
+
+
 def get_user_or_org(username):
   try:
     return User.get(User.username == username, User.robot == False)