add error handling

Author: nvdk

app.js

@@ -1,4 +1,4 @@
-import { app } from 'mu';
+import { app, errorHandler  } from 'mu';
 import services from './config/rules';
 import normalizeQuad from './config/normalize-quad';
 import bodyParser from 'body-parser';
@@ -68,6 +68,19 @@ app.post( '/', bodyParser.json({limit: '500mb'}), function( req, res ) {
   res.status(204).send();
 } );
 
+// log delta's ignored because of size
+app.use((err, req, res, next) => {
+  if (err.type === 'entity.too.large') {
+    console.warn(`Payload too large for ${req.method} ${req.originalUrl}`);
+    return res.status(413).send('Payload too large');
+  }
+
+  // Pass other errors to the default handler
+  next(err);
+});
+
+app.use(errorHandler);
+
 async function informWatchers( changeSets, res, muCallIdTrail, muSessionId ){
   // Iterate over each unique match pattern
   for (const matchKey in groupedServices) {