pgsql: Improve CREATE SUBSCRIPTION option parsing

Improve CREATE SUBSCRIPTION option parsing

When creating a subscription with slot_name = NONE, we failed to check
that also create_slot = false and enabled = false were set. This
created an invalid subscription and could later lead to a crash if a
NULL slot name was accessed. Add more checks around that for
robustness.

Reported-by: tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/62345698513cbcb3c48a6dae414abf0f24fd163a

Modified Files
--------------
src/backend/commands/subscriptioncmds.c | 14 +++++++++++++-
src/backend/replication/logical/worker.c | 9 +++++++++
src/test/regress/expected/subscription.out | 8 ++++++++
src/test/regress/sql/subscription.sql | 4 ++++
4 files changed, 34 insertions(+), 1 deletion(-)