Make request from app to get 401 instead of oauth redirect

[jvalkeal]

When angular app does a request it should get 401 instead of redirect for oauth login as app really can't handle it. There is a fix for this for non-webflux config spring-projects/spring-security#6812.

There's currently a hack to work around this as in a SecurityController we simply force 401 in exception handler which works as we force app to go into /oauth2/authorization/github when doing a login.

I'd just like oauth login to work as is if user manually goes to api methods.