Updated code to make it cleaner and easier to be used on other methods.
The most significant change was the definition of public variables to identify each authority group.
This changes makes it easier and safer the use of this variables by other methods, because it avoids the need of comparing strings containing the authority name. Now it compares GrantedAuthority's variables.
Signed-off-by: Bruno Nocera Zanette <firstname.lastname@example.org>