create GroupList type and methods

models/group/group_list.go

@@ -0,0 +1,17 @@
+package group
+
+import (
+	"context"
+)
+
+type GroupList []*Group
+
+func (groups GroupList) LoadOwners(ctx context.Context) error {
+	for _, g := range groups {
+		err := g.LoadOwner(ctx)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}