Fix parameter name in by_sender API

feedbackloop/views.py

@@ -26,7 +26,7 @@ def by_sender(sender):
 
 @app.route('/api/by_sender', methods=('POST',))
 def api_by_sender():
-    sender = request.json.name
+    sender = request.json.sender
     reports = FeedbackEntry.query.filter(
         FeedbackEntry.sender == sender).order_by(
             FeedbackEntry.timestamp.desc())