add space and finish item create/update mutations.

internal/slerrors/forbidden.go

@@ -0,0 +1,22 @@
+package slerrors
+
+type forbiddenError struct {
+	Message string
+}
+
+func (e *forbiddenError) Error() string {
+	return "forbidden: " + e.Message
+}
+
+func Forbidden(message string) error {
+	return &forbiddenError{Message: message}
+}
+
+func IsForbidden(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	_, ok := err.(*forbiddenError)
+	return ok
+}