Update ASB minimum permissions and explain

servicepulse/usage-config.md

@@ -49,6 +49,7 @@ To lock it down even further to the minimally required permissions, create a cus
                     "Microsoft.ServiceBus/namespaces/read",
                     "Microsoft.ServiceBus/namespaces/providers/Microsoft.Insights/metricDefinitions/read",
                     "Microsoft.ServiceBus/namespaces/queues/read",
+                    "Microsoft.Resources/subscriptions/read",
                     "Microsoft.Resources/subscriptions/resources/read"
                 ],
                 "notActions": [],
@@ -60,6 +61,8 @@ To lock it down even further to the minimally required permissions, create a cus
 }
 ```
 
+The `Microsoft.ServiceBus` permissions are required to read queue names and metric data from Azure Monitor. The `Microsoft.Resources/subscriptions` permissions are required in order to locate the Service Bus namespace within the Azure subscription.
+
 ### Amazon SQS
 
 #### Settings
@@ -133,4 +136,4 @@ If unable to fix the issue, open a [non-critical support case](https://particula
 Information that is considered sensitive can be obfuscated in the usage report.
 All words to be redacted can be specified in the `Mask Report Data` tab. Specify one word per line.
 
-![usage-setup-masks](images/usage-setup-masks.png "width=600")
+![usage-setup-masks](images/usage-setup-masks.png "width=600")