Merge pull request #58173 from rachel-msft/dblink

dblink support

Author: PRMerger12

articles/postgresql/concepts-extensions.md

@@ -83,6 +83,7 @@ The following tables list the standard PostgreSQL extensions that are currently
 | [pgstattuple](https://www.postgresql.org/docs/9.6/static/pgstattuple.html) | Provides a means for showing tuple-level statistics. |
 | [postgres\_fdw](https://www.postgresql.org/docs/9.6/static/postgres-fdw.html) | Foreign-data wrapper used to access data stored in external PostgreSQL servers. |
 | [hypopg](https://hypopg.readthedocs.io/en/latest/) | Provides a means of creating hypothetical indexes that don't cost CPU or disk. |
+| [dblink](https://www.postgresql.org/docs/current/dblink.html) | A module that supports connections to other PostgreSQL databases from within a database session. |
 
 
 ### PostGIS extensions