Azure: Add support for custom namespace and custom metrics variable queries (#99279)

* Add custom metric namespace and metric name queries

* Fix outdated type

* Support specifying custom

- Add custom support to getMetricNamespaces
- Ensure the customNamespace is specified in getMetricNames calls

* Update data source tests

* Support custom namespace/metrics variable queries

- Add tests

* Add fields to variable editor

- Update tests
- Update docs
- Update selectors

* Remove unneeded Promise.resolve

* Add comment

* Don't mutate expected path

* Lint

* Update docs/sources/datasources/azure-monitor/template-variables/index.md

Co-authored-by: Larissa Wandzura <126723338+lwandz13@users.noreply.github.com>

* Update docs/sources/datasources/azure-monitor/template-variables/index.md

Co-authored-by: Larissa Wandzura <126723338+lwandz13@users.noreply.github.com>

* Update docs

* Update conditionals

* Lint

---------

Co-authored-by: Larissa Wandzura <126723338+lwandz13@users.noreply.github.com>

pkg/tsdb/azuremonitor/kinds/dataquery/types_dataquery_gen.go

@@ -28,6 +28,7 @@ type AzureMonitorQuery struct {
 	// TODO make this required and give it a default
 	QueryType *string `json:"queryType,omitempty"`
 	// Azure subscription containing the resource(s) to be queried.
+	// Also used for template variable queries
 	Subscription *string `json:"subscription,omitempty"`
 	// Subscriptions to be queried via Azure Resource Graph.
 	Subscriptions []string `json:"subscriptions,omitempty"`
@@ -41,11 +42,16 @@ type AzureMonitorQuery struct {
 	AzureTraces *AzureTracesQuery `json:"azureTraces,omitempty"`
 	// @deprecated Legacy template variable support.
 	GrafanaTemplateVariableFn *GrafanaTemplateVariableQuery `json:"grafanaTemplateVariableFn,omitempty"`
-	// Template variables params. These exist for backwards compatiblity with legacy template variables.
+	// Resource group used in template variable queries
 	ResourceGroup *string `json:"resourceGroup,omitempty"`
-	Namespace     *string `json:"namespace,omitempty"`
-	Resource      *string `json:"resource,omitempty"`
-	Region        *string `json:"region,omitempty"`
+	// Namespace used in template variable queries
+	Namespace *string `json:"namespace,omitempty"`
+	// Resource used in template variable queries
+	Resource *string `json:"resource,omitempty"`
+	// Region used in template variable queries
+	Region *string `json:"region,omitempty"`
+	// Custom namespace used in template variable queries
+	CustomNamespace *string `json:"customNamespace,omitempty"`
 	// For mixed data sources the selected datasource is on the query level.
 	// For non mixed scenarios this is undefined.
 	// TODO find a better way to do this ^ that's friendly to schema
@@ -77,6 +83,8 @@ const (
 	AzureQueryTypeLocationsQuery            AzureQueryType = "Azure Regions"
 	AzureQueryTypeGrafanaTemplateVariableFn AzureQueryType = "Grafana Template Variable Function"
 	AzureQueryTypeTraceExemplar             AzureQueryType = "traceql"
+	AzureQueryTypeCustomNamespacesQuery     AzureQueryType = "Azure Custom Namespaces"
+	AzureQueryTypeCustomMetricNamesQuery    AzureQueryType = "Azure Custom Metric Names"
 )
 
 type AzureMetricQuery struct {