Feature/postgres connection names (#1998)

* avoid reindexing secondary indexes after they succeed

* use postgres application names to facilitate connection debugging

* centralize all postgres application_name constants in the constants file

* missed a couple of files

* mypy fixes

* update dev background script

backend/scripts/dev_run_background_jobs.py

@@ -24,7 +24,7 @@ def run_jobs(exclude_indexing: bool) -> None:
         "ee.danswer.background.celery.celery_app",
         "worker",
         "--pool=threads",
-        "--concurrency=16",
+        "--concurrency=6",
         "--loglevel=INFO",
     ]