Warning: Missing boundary in multipart/form-data POST data in Unknown on line 0
You have to just remove the following line:
ajax.setRequestHeader("Content-Type", "multipart/form-data");
Instead of sending the data as multipart/form-data:
ajax.setRequestHeader("Content-Type", "multipart/form-data");You should send it as application/json:
ajax.setRequestHeader("Content-Type", "application/json");