add user crud interface in impl

internal/user/service.go

@@ -0,0 +1,36 @@
+package user
+
+import "fmt"
+
+type Service struct {
+	store UserCRUD
+}
+
+func NewService(store UserCRUD) (UserCRUD, error) {
+	if store == nil {
+		return nil, fmt.Errorf("store is nil")
+	}
+	return &Service{
+		store: store,
+	}, nil
+}
+
+func (s *Service) Create(user *User) error {
+	return s.store.Create(user)
+}
+
+func (s *Service) GetByID(id int64) (*User, error) {
+	return s.store.GetByID(id)
+}
+
+func (s *Service) GetByUsername(username string) (*User, error) {
+	return s.store.GetByUsername(username)
+}
+
+func (s *Service) Update(user *User) error {
+	return s.store.Update(user)
+}
+
+func (s *Service) Delete(id int64) error {
+	return s.store.Delete(id)
+}