accept and content type
Content-Type header is used in POST , PUT , PATCH to specify
the type of body you are sending to the serve and it's required.
`Accept Header` can be used to ask the server to return
different type of response format
For example :
`/api/xname` endpoint , support both xml and json
as response type so we can add accept header
`application/xml` to get xml result and `application/json` result.
If server does not support such type ,
it will return `406 not acceptable` status code.