Provide a getAllUserRoles method

Nobody has claimed this yet.

The Servlet API offers a method to retrieve the current user's principal (HttpServletRequest#getUserPrincipal) and a method that can be used to determine if the current user has a specific role (HttpServletRequest#isUserInRole).

There is however no corresponding method or way to retrieve a list with all roles that the current user has in a portable way. There is potentially a way to do this via JACC, but that's not exactly a straightforward way, plus JACC is not universally available in Servlet containers. A use case for this is e.g. displaying to the user a list of all roles he or she has, or the ability to input such a list of roles into a custom authorization system.

I would be great if such a method could be added.

Start with the Servlet API entry points HttpServletRequest#getUserPrincipal and HttpServletRequest#isUserInRole, then review the issue discussion and any existing role-related API contracts. The work is complete when the project has an agreed portable way to retrieve all roles for the current user, with corresponding specification and compatibility tests.

Written by the indexing model from the issue text.