I am experiencing the funny phenomenon, that internet explorer converts a post login request to a get request, thus losing the credentials and redirecting to the login page without authenticating.
The functionality is correct for other browsers. I have successfully tested it with firefox, chrome, vivaldi and safari.
The loginAction method as done per this documentation: https://gist.github.com/rawroland/9929df558e66ed104c186fd309755069
The twig code for the login page: https://gist.github.com/rawroland/c53af4378dbe1547f862683b55d3bc21
The generated html code of the login page: https://gist.github.com/rawroland/f3cfdfc74a728dc648189e3931d8f827