Fix standard has_perm calls

[Vsevolod Novikov]

Fix standard has_perm calls to be compatible with packages checking permissions using has_perm call.

There may be a package using calls to the User.has_perm

Probably the own authentication backend should be implemented.

[Vsevolod Novikov]

The modified authentication backend has been implemented

[Vsevolod Novikov]

Tests added, the package has been issued