pgsql: Doc: add a summary table to the CREATE POLICY docs.

Doc: add a summary table to the CREATE POLICY docs.

This table summarizes which RLS policy expressions apply to each
command type, and whether they apply to the old or new tuples (or
both), which saves reading through a lot of text.

Rod Taylor, hacked on by me. Reviewed by Fabien Coelho.

Discussion: https://postgr.es/m/CAHz80e4HxJShm6m9ZWFrHW=pgd2KP=RZmfFnEccujtPMiAOW5Q@mail.gmail.com

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/1a164f940b10ad327548c747f4c45e83906784ba

Modified Files
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doc/src/sgml/ref/create_policy.sgml | 104 +++++++++++++++++++++++++++++++++++-
1 file changed, 103 insertions(+), 1 deletion(-)