Support dashboard restore across API versions (#110694)

What

This commit refactors the logic to restore a dashboard from a version.
The logic is moved from the API handler to the dashboard versions service,
which now supports restoring dashboards of different API versions.

Why

To make sure that dashboard version restoration works with v2 dashboards
API, as well as future API versions.

Signed-off-by: Igor Suleymanov <igor.suleymanov@grafana.com>

pkg/services/dashboardversion/dashvertest/fake.go

@@ -3,6 +3,7 @@ package dashvertest
 import (
 	"context"
 
+	"github.com/grafana/grafana/pkg/services/dashboards"
 	dashver "github.com/grafana/grafana/pkg/services/dashboardversion"
 )
 
@@ -13,6 +14,10 @@ type FakeDashboardVersionService struct {
 	ExpectedContinueToken        string
 	counter                      int
 	ExpectedError                error
+	// New fields for RestoreVersion testing
+	ExpectedRestoreResult *dashboards.Dashboard
+	RestoreVersionCalled  bool
+	LastRestoreCommand    *dashver.RestoreVersionCommand
 }
 
 func NewDashboardVersionServiceFake() *FakeDashboardVersionService {
@@ -37,3 +42,9 @@ func (f *FakeDashboardVersionService) List(ctx context.Context, query *dashver.L
 		Versions:      f.ExpectedListDashboarVersions,
 	}, f.ExpectedError
 }
+
+func (f *FakeDashboardVersionService) RestoreVersion(ctx context.Context, cmd *dashver.RestoreVersionCommand) (*dashboards.Dashboard, error) {
+	f.RestoreVersionCalled = true
+	f.LastRestoreCommand = cmd
+	return f.ExpectedRestoreResult, f.ExpectedError
+}