AzureMonitor: Explain custom and metric namespace properties (#55048)

public/app/plugins/datasource/grafana-azure-monitor-datasource/components/ResourcePicker/Advanced.tsx

@@ -86,7 +86,7 @@ const Advanced = ({ resource, onChange }: ResourcePickerProps<string | AzureMetr
               />
             </InlineField>
             <InlineField
-              label="Metric Namespace"
+              label="Namespace"
               grow
               transparent
               htmlFor="input-advanced-resource-picker-metricNamespace"

public/app/plugins/datasource/grafana-azure-monitor-datasource/types/query.ts

@@ -45,8 +45,12 @@ export interface AzureMonitorQuery extends DataQuery {
 export interface AzureMetricQuery {
   resourceGroup?: string;
   resourceName?: string;
-  /** Resource type */
+  /** metricNamespace is used as the resource type (or resource namespace).
+   * It's usually equal to the target metric namespace.
+   * Kept the name of the variable as metricNamespace to avoid backward incompatibility issues.
+   */
   metricNamespace?: string;
+  /** used as the value for the metricNamespace param when different from the resource namespace */
   customNamespace?: string;
   metricName?: string;
   timeGrain?: string;