pgsql: postgres_fdw: Make postgres_fdw.application_name support more es

postgres_fdw: Make postgres_fdw.application_name support more escape sequences.

Commit 6e0cb3dec1 allowed postgres_fdw.application_name to include
escape sequences %a (application name), %d (database name), %u (user name)
and %p (pid). In addition to them, this commit makes it support
the escape sequences for session ID (%c) and cluster name (%C).
These are helpful to investigate where each remote transactions came from.

Author: Fujii Masao
Reviewed-by: Ryohei Takahashi, Kyotaro Horiguchi
Discussion: https://postgr.es/m/1041dc9a-c976-049f-9f14-e7d94c29c4b2@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/94c49d53402240ad7ddbcae9049ff2840a54b9c6

Modified Files
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contrib/postgres_fdw/expected/postgres_fdw.out | 20 ++++++++++++++++++++
contrib/postgres_fdw/option.c | 6 ++++++
contrib/postgres_fdw/sql/postgres_fdw.sql | 11 +++++++++++
doc/src/sgml/postgres-fdw.sgml | 14 ++++++++++++++
src/include/utils/guc.h | 2 +-
5 files changed, 52 insertions(+), 1 deletion(-)