Add selectable PostgreSQL monitor backends

plugins/postgresql/manifest.json

@@ -1,6 +1,6 @@
 {
   "name": "postgresql",
-  "version": 4,
+  "version": 5,
   "module": "plugin.py",
   "actions": [
     "monitor",
@@ -20,6 +20,10 @@
   ],
   "optional_config": [
     "PG_RECONNECT_GRACE_SECONDS",
-    "PACEMAKER_NODE_NAME"
+    "PACEMAKER_NODE_NAME",
+    "MONITOR_BACKEND",
+    "CONTAINER_RUNTIME",
+    "CONTAINER_NAME",
+    "PG_OS_USER"
   ]
 }