Improve logging when sending events (#883)

We have some failing sytests on sqlite but it's very difficult to debug
due to lack of useful logging. This adds a log line for when a new event
is sent (incl. logging the event ID) as well as adding a user_id field
for all contextual logs so we know who initiated certain actions.

common/httpapi.go

@@ -25,6 +25,10 @@ func MakeAuthAPI(
 		if err != nil {
 			return *err
 		}
+		// add the user ID to the logger
+		logger := util.GetLogger((req.Context()))
+		logger = logger.WithField("user_id", device.UserID)
+		req = req.WithContext(util.ContextWithLogger(req.Context(), logger))
 
 		return f(req, device)
 	}