[bradm] Add nagios-context to config.yaml

config.yaml

@@ -94,3 +94,13 @@ options:
     default: False
     type: boolean
     description: Enable debug logging
+  nagios_context:
+    default: "juju"
+    type: string
+    description: |
+        Used by the nrpe-external-master subordinate charm.
+        A string that will be prepended to instance name to set the host name
+        in nagios. So for instance the hostname would be something like:
+            juju-postgresql-0
+        If you're running multiple environments with the same services in them
+        this allows you to differentiate between them.