Add support for RLS policies to be 'PERMISSIVE' or 'RESTRICTIVE'.

[rohangaonk]

currently there is no support for policies to be 'RESTRICTIVE'. By default policies are 'PERMISSIVE', it would be good to have an additional option when defining policy. currently in my project i am using raw query to achieve this. Thanks!!

[nealoke]

+1 for this, would be great 😍

[Shinigami92]

@nealoke are you interested in doing a PR?