Create and test CORS example headers

[M4GNV5]

Is your feature request related to a problem? Please describe. The current THI API does not have CORS. The future test THI API has CORS, which was added using code we provided. Yesterday we found out the code does not fully work. It seems completely broken in Firefox and is furthermore missing allowed-headers which are required by the new API.

Describe the solution you'd like In order to give proper code to THI for incorperating into their API we should test the CORS PHP code ourself with different browsers before giving it to them.

Additional context old code we provided:

if ($_SERVER['HTTP_ORIGIN'] == 'https://neuland.app' || $_SERVER['HTTP_ORIGIN'] == 'https://dev.neuland.app') {
  header('Access-Control-Allow-Origin: ' . $_SERVER['HTTP_ORIGIN']);
  header('Access-Control-Max-Age: 7200');
}

Firefox CORS error (even though the header is provided):

Chrome CORS error because of missing allow-headers:

[M4GNV5]

I had a phone call with Mr. Z yesterday. Apparently they configured the CORS options using their webserver and did not use our PHP code. This means we probably do not need to provide PHP code, but we do need to test and provide actually working header options.