Alerting: Allow selection of recording rule write target on per-rule basis. (#101778)

* Alerting: Allow selection of recording rule write target on per-rule basis.

Introduces a new feature flag (`grafanaManagedRecordingRulesDatasources`),
disabled by default, to enable the ability to write recording rules data using
data source settings, and selecting the data source to use on a per-rule basis.

To cope with the scenario of users upgrading, a configuration file option
allows setting the default data source to use, if none is specified in the rule,
emulating the behaviour of recording rules without the flag enabled.

* Lint

* Update conf/sample.ini

Co-authored-by: Alexander Akhmetov <me@alx.cx>

---------

Co-authored-by: Alexander Akhmetov <me@alx.cx>

pkg/services/featuremgmt/registry.go

@@ -1790,6 +1790,15 @@ var (
 			Owner:       grafanaAlertingSquad,
 			Expression:  "true", // enabled by default
 		},
+		{
+			Name:              "grafanaManagedRecordingRulesDatasources",
+			Description:       "Enables writing to data sources for Grafana-managed recording rules.",
+			Stage:             FeatureStageExperimental,
+			Owner:             grafanaAlertingSquad,
+			AllowSelfServe:    false,
+			HideFromAdminPage: true,
+			HideFromDocs:      true,
+		},
 	}
 )
 

pkg/services/featuremgmt/toggles_gen.csv

@@ -237,3 +237,4 @@ newShareReportDrawer,experimental,@grafana/sharing-squad,false,false,false
 rendererDisableAppPluginsPreload,experimental,@grafana/sharing-squad,false,false,true
 assetSriChecks,experimental,@grafana/frontend-ops,false,false,true
 alertRuleRestore,preview,@grafana/alerting-squad,false,false,false
+grafanaManagedRecordingRulesDatasources,experimental,@grafana/alerting-squad,false,false,false

pkg/services/featuremgmt/toggles_gen.go

@@ -958,4 +958,8 @@ const (
 	// FlagAlertRuleRestore
 	// Enables the alert rule restore feature
 	FlagAlertRuleRestore = "alertRuleRestore"
+
+	// FlagGrafanaManagedRecordingRulesDatasources
+	// Enables writing to data sources for Grafana-managed recording rules.
+	FlagGrafanaManagedRecordingRulesDatasources = "grafanaManagedRecordingRulesDatasources"
 )

pkg/services/featuremgmt/toggles_gen.json

@@ -1964,6 +1964,20 @@
         "hideFromDocs": true
       }
     },
+    {
+      "metadata": {
+        "name": "grafanaManagedRecordingRulesDatasources",
+        "resourceVersion": "1741291902441",
+        "creationTimestamp": "2025-03-06T20:11:42Z"
+      },
+      "spec": {
+        "description": "Enables writing to data sources for Grafana-managed recording rules.",
+        "stage": "experimental",
+        "codeowner": "@grafana/alerting-squad",
+        "hideFromAdminPage": true,
+        "hideFromDocs": true
+      }
+    },
     {
       "metadata": {
         "name": "grafanaconThemes",