fix: Makes created and updated by nullable strings for library panel migration (#108122)

Signed-off-by: Bruno Abrantes <bruno@brunoabrantes.com>

pkg/registry/apis/dashboard/legacy/sql_dashboards.go

@@ -489,10 +489,10 @@ type panel struct {
 	FolderUID sql.NullString
 
 	Created   time.Time
-	CreatedBy string
+	CreatedBy sql.NullString
 
 	Updated   time.Time
-	UpdatedBy string
+	UpdatedBy sql.NullString
 
 	Version int64
 
@@ -633,13 +633,13 @@ func parseLibraryPanelRow(p panel) (dashboardV0.LibraryPanel, error) {
 	if p.FolderUID.Valid {
 		meta.SetFolder(p.FolderUID.String)
 	}
-	meta.SetCreatedBy(p.CreatedBy)
+	meta.SetCreatedBy(getUserID(p.CreatedBy, sql.NullInt64{}))
 	meta.SetGeneration(p.Version)
 	meta.SetDeprecatedInternalID(p.ID) //nolint:staticcheck
 
 	// Only set updated metadata if it is different
-	if p.UpdatedBy != p.CreatedBy || p.Updated.Sub(p.Created) > time.Second {
-		meta.SetUpdatedBy(p.UpdatedBy)
+	if p.UpdatedBy.Valid && p.Updated.Sub(p.Created) > time.Second {
+		meta.SetUpdatedBy(getUserID(p.UpdatedBy, sql.NullInt64{}))
 		meta.SetUpdatedTimestamp(&p.Updated)
 	}