Analytics: Instrument Azure Application Insights (#38553)

* add backend

* read config and pass to backend

* update config docs

* change var name

* use connection string instead of instrumentation key

* add config for endpoint url. update docs

* update default ini

* add spaces

* remove space

* Update docs/sources/administration/configuration.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* Update conf/defaults.ini

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* Update conf/defaults.ini

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/setting/setting.go

@@ -369,9 +369,11 @@ type Cfg struct {
 	Env string
 
 	// Analytics
-	CheckForUpdates      bool
-	ReportingDistributor string
-	ReportingEnabled     bool
+	CheckForUpdates                     bool
+	ReportingDistributor                string
+	ReportingEnabled                    bool
+	ApplicationInsightsConnectionString string
+	ApplicationInsightsEndpointUrl      string
 
 	// LDAP
 	LDAPEnabled     bool
@@ -908,6 +910,8 @@ func (cfg *Cfg) Load(args CommandLineArgs) error {
 	if len(cfg.ReportingDistributor) >= 100 {
 		cfg.ReportingDistributor = cfg.ReportingDistributor[:100]
 	}
+	cfg.ApplicationInsightsConnectionString = analytics.Key("application_insights_connection_string").String()
+	cfg.ApplicationInsightsEndpointUrl = analytics.Key("application_insights_endpoint_url").String()
 
 	if err := readAlertingSettings(iniFile); err != nil {
 		return err