adding or replacing sort params for provider urls when necessary

lib/services/queryStringMutator.js

@@ -0,0 +1,22 @@
+const queryString = require('query-string');
+
+/**
+ * for Fredy, it is important to sort search results by date, starting with the latest listing. if it is not sorted, we
+ * might never actually find the newest results, no matter how many pages we crawl.
+ * It has been written in the documentation, but obviously nobody reads docu theses days which is why it's been done
+ * automagically now.
+ *
+ * @param _url actual provider url containing the searchParams
+ * @param sortByDateParam param(s) indicating the correct sort order
+ * @returns {`${string}?${string}`} correctly formatted url
+ */
+module.exports = (_url, sortByDateParam) => {
+  //if no mutation is necessary, just return the original url
+  if (sortByDateParam == null) {
+    return _url;
+  }
+
+  const original = queryString.parseUrl(_url);
+  const mutate = queryString.parse(sortByDateParam);
+  return `${original.url}?${queryString.stringify({ ...original.query, ...mutate })}`;
+};