Log out token to audit log

We need to know who tried to do something as well as what they were
trying to do for these logs to be useful.

backdrop/write/api.py

@@ -351,6 +351,7 @@ def audit_append(data_set_name, data):
     if data:
         start_at, end_at = parse_bounding_dates(data)
         extra = {
+            'token': request.headers.get('Authorization'),
             'data_set': data_set_name,
             'start_at': start_at,
             'end_at': end_at,
@@ -361,7 +362,8 @@ def audit_append(data_set_name, data):
 
 def audit_delete(data_set_name):
     app.audit_logger.info("Data delete action", extra={
-        'data_set': data_set_name
+        'token': request.headers.get('Authorization'),
+        'data_set': data_set_name,
     })