fix(api): allow disabling named Postgres prepared statements (#2251)

deploy/self-hosting/.env.example

@@ -113,3 +113,10 @@ FLUXER_DISCOVERY_ENABLED=true
 # from starting far more schedulers than the container can actually use.
 #FLUXER_ERLANG_SCHEDULERS_MIN=2
 #FLUXER_ERLANG_SCHEDULERS_MAX=16
+
+# The api names its fixed Postgres statement shapes so the server can reuse their
+# plans. Named prepared statements require a session that outlives the
+# transaction, so set this to false if you put a transaction-pooling connection
+# pooler such as PgBouncer in front of Postgres. The bundled compose talks to
+# Postgres directly, where naming is a win and the default is correct.
+#FLUXER_POSTGRES_PREPARED_STATEMENTS=true