Emit a warning if the extension's GUC is set incorrectly

[Shinya Kato]

Hi hackers,

If wrong GUCs of auth_delay, pg_trgm, postgres_fdw and sepgsql are 
described in postgresql.conf, a warning is not emitted unlike 
pg_stat_statements, auto_explain and pg_prewarm.
So, I improved it by adding EmitWarningsOnPlaceholders.
An example output is shown below.
---
2021-11-14 18:18:16.486 JST [487067] WARNING:  unrecognized 
configuration parameter "auth_delay.xxx"
---
What do you think?

--
Regards,

--
Shinya Kato
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATIONdiff --git a/contrib/auth_delay/auth_delay.c b/contrib/auth_delay/auth_delay.c
index 5820ac328d..d11dd1e416 100644
--- a/contrib/auth_delay/auth_delay.c
+++ b/contrib/auth_delay/auth_delay.c
@@ -67,6 +67,9 @@ _PG_init(void)
 							NULL,
 							NULL,
 							NULL);
+
+	EmitWarningsOnPlaceholders("auth_delay");
+
 	/* Install Hooks */
 	original_client_auth_hook = ClientAuthentication_hook;
 	ClientAuthentication_hook = auth_delay_checks;
diff --git a/contrib/pg_trgm/trgm_op.c b/contrib/pg_trgm/trgm_op.c
index fb38135f7a..0407c7dd64 100644
--- a/contrib/pg_trgm/trgm_op.c
+++ b/contrib/pg_trgm/trgm_op.c
@@ -100,6 +100,8 @@ _PG_init(void)
 							 NULL,
 							 NULL,
 							 NULL);
+
+	EmitWarningsOnPlaceholders("pg_trgm");
 }
 
 /*
diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c
index 48c7417e6e..36555398ec 100644
--- a/contrib/postgres_fdw/option.c
+++ b/contrib/postgres_fdw/option.c
@@ -469,4 +469,6 @@ _PG_init(void)
 							   NULL,
 							   NULL,
 							   NULL);
+
+	EmitWarningsOnPlaceholders("postgres_fdw");
 }
diff --git a/contrib/sepgsql/hooks.c b/contrib/sepgsql/hooks.c
index 19a3ffb7ff..44a09c35a7 100644
--- a/contrib/sepgsql/hooks.c
+++ b/contrib/sepgsql/hooks.c
@@ -455,6 +455,8 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
+	EmitWarningsOnPlaceholders("sepgsql");
+
 	/* Initialize userspace access vector cache */
 	sepgsql_avc_init();