fix: parse method mutating its input

Author: matejvasek

src/lib/bindings/http/validation/structured.js

@@ -32,17 +32,20 @@ function parse(payload, headers, receiver) {
     source: undefined
   };
 
+
+  const unprocessed = new Set(Object.keys(incoming));
+
   receiver.parserMap.forEach((value, key) => {
     if (incoming[key]) {
       event[value.name] = value.parser(incoming[key]);
-      delete incoming[key];
+      unprocessed.delete(key);
     }
   });
 
   const cloudevent = new CloudEvent(event);
 
   // Every unprocessed attribute should be an extension
-  Array.from(Object.keys(incoming)).forEach((extension) =>
+  unprocessed.forEach((extension) =>
     cloudevent.addExtension(extension, incoming[extension]));
 
   cloudevent.spec.check();