Consider replacing an inner loop with Set of authority strings in AuthorityAuthorizationManager#isAuthorized

[evgeniycheban]

Currently AuthorityAuthorizationManager#isAuthorized uses an inner loop to determine if user has required authority:

private boolean isAuthorized(Authentication authentication) {
    for (GrantedAuthority grantedAuthority : authentication.getAuthorities()) {
	for (GrantedAuthority authority : this.authorities) {
	    if (authority.getAuthority().equals(grantedAuthority.getAuthority())) {
		return true;
            }
	}
    }
    return false;
}

It can be replaced with a Set of authority strings which will be more efficient because HashSet has constant lookup time O(1).

[evgeniycheban]

@jzheaux I've just found AuthorityUtils#authorityListToSet method that does the same I did in getAuthoritySet, can I open another PR that will add this minor change?