fix: report resource conflicts and accurate CLI API errors

back/middlewares/uniqueConstraintError.ts

@@ -0,0 +1,14 @@
+import { ErrorRequestHandler } from 'express';
+import { UniqueConstraintError } from 'sequelize';
+import { t } from '../shared/i18n';
+
+// Handle the database constraint itself so concurrent writes are covered too.
+const uniqueConstraintError: ErrorRequestHandler = (err, req, res, next) => {
+  if (!(err instanceof UniqueConstraintError)) return next(err);
+  // Constraint details can contain environment values or application credentials.
+  res
+    .status(409)
+    .json({ code: 409, message: t('资源已存在，请检查重复的名称或值') });
+};
+
+export default uniqueConstraintError;