Add TODO

Author: brunorijsman

TODO

@@ -61,4 +61,6 @@ TODO: Testcase for invalid signature
 
 TODO: Test case for: if signature validation fails, return fragment to pool
 
-TODO: Error message if --client or --hub does not exist in topology
+TODO: Error message if --client or --hub does not exist in topology
+
+TODO: Check SAE IDs on GET share, just as we do for POST share