pgsql: Warn if wal_level is too low when creating a publication.

Warn if wal_level is too low when creating a publication.

Provide a hint to users that they need to increase wal_level before
subscriptions can work.

Author: Lucas Viecelli, with some adjustments by Thomas Munro
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAPjy-57rn5Y9g4e5u--eSOP-7P4QrE9uOZmT2ZcUebF8qxsYhg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b31fbe852c095a827caade2e0702f8a215053bea

Modified Files
--------------
src/backend/commands/publicationcmds.c       |  8 ++++++++
src/test/regress/expected/object_address.out |  3 +++
src/test/regress/expected/publication.out    | 13 +++++++++++++
src/test/regress/sql/object_address.sql      |  3 +++
src/test/regress/sql/publication.sql         | 13 +++++++++++++
5 files changed, 40 insertions(+)