Ok. I found problem.
It was not on the Angular side. To be honest, there were no problem at all.
Reason why I was unable to perform my request succesfuly was that my server app was not properly handling OPTIONS request.
Why OPTIONS, not POST? My server app is on different host, then frontend. Because of CORS my browser was converting POST to OPTION: http://restlet.com/blog/2015/12/15/understanding-and-using-cors/
With help of this answer: Standalone Spring OAuth2 JWT Authorization Server + CORS
I implemented proper filter on my server-side app.
Thanks to @Supamiu - the person which fingered me that I am not sending POST at all.