Add state migration function

For resources with the "Name" identifier

routeros/provider_resource_state_migration.go

@@ -0,0 +1,35 @@
+package routeros
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+func stateMigrationNameToId(resourcePath string) schema.StateUpgradeFunc {
+	return func(ctx context.Context, rawState map[string]interface{}, m interface{}) (map[string]interface{}, error) {
+		ColorizedMessage(ctx, INFO, fmt.Sprintf("ID attribute before migration: %#v", rawState["id"]))
+
+		if rawState["id"] != nil {
+			res, err := ReadItems(&ItemId{Name, rawState["id"].(string)}, resourcePath, m.(Client))
+			if err != nil {
+				return nil, err
+			}
+
+			// Resource not found.
+			if len(*res) == 0 {
+				rawState["id"] = ""
+				ColorizedMessage(ctx, WARN, "No resource found, but the scheme has been updated.",
+					map[string]interface{}{"path": resourcePath, "id": rawState["id"]})
+				return rawState, nil
+			}
+
+			rawState["id"] = (*res)[0].GetID(Id)
+		}
+
+		ColorizedMessage(ctx, INFO, fmt.Sprintf("ID attribute after migration: %#v", rawState["id"]))
+
+		return rawState, nil
+	}
+}