I'm trying to POST my local storage to an API, but everytime I do it, I get a status: 400. Title of error says '"One or more validation errors occurred."'

I must be doing this wrong. I'm trying to loop through all the key value pairs and then send that via a POST.

  public postInfo() {
    for (let i = 0; i < localStorage.length; i++) {
      const key = localStorage.key(i);

    const headerDict = {
      'Content-Type': 'application/json',
      'Accept': 'application/json',
      'Access-Control-Allow-Headers': 'Content-Type',

    const requestOptions = {
      headers: new HttpHeaders(headerDict),

      this.http.post(this.url, key, requestOptions).subscribe(data => {
Also here is how I'm saving my local storage:

addToCart(product: Product) {
    var sendJson = JSON.stringify(product.productID);
    var jsonData = JSON.stringify(product.productName)
    localStorage.setItem(sendJson, jsonData);