fix(httpclient): pass query params as object for smartrequest compatibility

ts/bunq.classes.httpclient.ts

@@ -53,13 +53,13 @@ export class BunqHttpClient {
     };
 
     if (options.params) {
-      const params = new URLSearchParams();
+      const queryParams: { [key: string]: string } = {};
       Object.entries(options.params).forEach(([key, value]) => {
         if (value !== undefined && value !== null) {
-          params.append(key, String(value));
+          queryParams[key] = String(value);
         }
       });
-      requestOptions.queryParams = params.toString();
+      requestOptions.queryParams = queryParams;
     }
 
     try {