title: preflight request triggers based on content-type
body: <p>Recently, I was reading about preflight request(OPTIONS) and got to know that it is always triggered when content-type is "application/json" or some other except "text/plain" ,"application/x-www-form-urlencoded" &amp; "multipart/form-data Content-Types"</p>
  
  <p>So my question is why it is always getting triggered for specific content-type like "application/json" not for above mentioned content-type .</p>