start work on invite keys

app/__init__.py

@@ -139,6 +139,11 @@ def bind_default_badges(path):
                     'uploaded_at': int(os.path.getmtime(real_path)),
                 })
 
+def clear_stale_invites():
+    from .db import db
+    from .util import time_now
+    db.execute('DELETE FROM "invite_keys" WHERE expires_at < ?', time_now())
+
 def clear_stale_sessions():
     from .db import db
     with db.transaction():
@@ -234,6 +239,7 @@ def create_app():
 
         clear_stale_sessions()
         clear_api_limits()
+        clear_stale_invites()
 
         reparse_babycode()