test_rls_hooks is an example of how to use the hooks provided for RLS to
define additional policies to be used.

Functions
=========
test_rls_hooks_permissive(CmdType cmdtype, Relation relation)
    RETURNS List*

Returns a list of policies which should be added to any existing
policies on the relation, combined with OR.

test_rls_hooks_restrictive(CmdType cmdtype, Relation relation)
    RETURNS List*

Returns a list of policies which should be added to any existing
policies on the relation, combined with AND.