Alerting: Extend recording rule definitions/interfaces with data source. (#101678)

Extend the recording rule definition to include the target data source, allowing
configuration of where the output of the recording rule is written to. Also
extends the relevant interfaces in preparation for the next set of changes.

pkg/services/ngalert/api/tooling/definitions/cortex-ruler.go

@@ -533,6 +533,10 @@ type Record struct {
 	// required: true
 	// example: A
 	From string `json:"from" yaml:"from"`
+	// Which data source should be used to write the output of the recording rule, specified by UID.
+	// required: false
+	// example: my-prom
+	TargetDatasourceUID string `json:"target_datasource_uid,omitempty" yaml:"target_datasource_uid,omitempty"`
 }
 
 // swagger:model

pkg/services/ngalert/api/tooling/definitions/provisioning_alert_rules.go

@@ -308,6 +308,7 @@ type AlertRuleNotificationSettingsExport struct {
 
 // Record is the provisioned export of models.Record.
 type AlertRuleRecordExport struct {
-	Metric string `json:"metric" yaml:"metric" hcl:"metric"`
-	From   string `json:"from" yaml:"from" hcl:"from"`
+	Metric              string  `json:"metric" yaml:"metric" hcl:"metric"`
+	From                string  `json:"from" yaml:"from" hcl:"from"`
+	TargetDatasourceUID *string `json:"targetDatasourceUid,omitempty" yaml:"targetDatasourceUid,omitempty" hcl:"target_datasource_uid,optional"`
 }