SQL std auth - support,authorize new 'show grant..' statements

SHOW GRANTS statement -
It will give a list of objects, privileges, and who granted the grantee rights on that object

• When used by a user who does not participate in the SUPERUSER role, it can be
  used in three ways
  • SHOW GRANTS; This will show all grants effective for the current user or
    roles, whichever is currently determining the user’s privileges.
  • SHOW GRANTS FOR role; This will show grants effective for a given
    role. The user must participate in that role, otherwise permission will be
    denied.
  • SHOW GRANTS FOR user; where user is the username of the current
    user. This will show grants effective for the user. Attempts to list grants
    effective for other users will be denied.
• When used by a user who does participate in the SUPERUSER role, it can be
  used in three ways:
  • SHOW GRANTS; As in the previous section.
  • SHOW GRANTS FOR role; This will show grants effective for a given
    role. Any role, regardless of whether the current user participates in it,
    can be shown.
  • SHOW GRANTS FOR user; where user is a valid username. This will
    show grants effective for that user. Any user, regardless of whether it is
    the current user, can be shown

Task includes authorization of the statement.