UIDInAnyGroup returns true if the user with supplied uid is a member of any group in list.
List is a string slice that may contain GIDs, groupnames, or both.
UIDInList returns true if the user with supplied uid is in list (match by uid or username).
List is a string slice that may contain UIDs, usernames, or both.
CurrentOriginal returns a pointer to User structure associated with the
original current user, if current user is inside a user namespace with a
custom user mappings, it will returns information about the original user
otherwise it returns information about the current user