pgsql: Change SQLSTATE for event triggers "wrong context" message

Change SQLSTATE for event triggers "wrong context" message

When certain event-trigger-only functions are called when not in the
wrong context, they were reporting the "feature not supported" SQLSTATE,
which is somewhat misleading. Create a new custom error code for such
uses instead.

Not backpatched since it may be seen as an undesirable behavioral
change.

Author: Michael Paquier
Discussion: https://www.postgresql.org/message-id/CAB7nPqQ-5NAkHQHh_NOm7FPep37NCiLKwPoJ2Yxb8TDoGgbYYA@mail.gmail.com

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/73206812cd97436cffd8f331dbb09d38a2728162

Modified Files
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src/backend/commands/event_trigger.c | 6 +++---
src/backend/utils/errcodes.txt | 1 +
2 files changed, 4 insertions(+), 3 deletions(-)