fix(identity): return 400 with specific reasons on registration failure

clients/admin/package.json

@@ -52,5 +52,8 @@
   },
   "engines": {
     "node": ">=20"
+  },
+  "overrides": {
+    "esbuild": "^0.28.1"
   }
 }

clients/admin/src/components/users/create-user-dialog.tsx

@@ -18,7 +18,7 @@ import {
   DialogBody,
   DialogFooter,
 } from "@/components/ui/dialog";
-import { ApiRequestError } from "@/lib/api-client";
+import { describeError } from "@/lib/api-client";
 
 // ─── Schema (identical to the old create page) ───────────────────────────────
 
@@ -124,11 +124,7 @@ export function CreateUserDialog({
       navigate(result.userId ? `/users/${result.userId}` : "/users");
     },
     onError: (err) => {
-      const detail =
-        err instanceof ApiRequestError
-          ? err.problem?.detail ?? err.problem?.title ?? err.message
-          : (err as Error).message;
-      toast.error("Create failed", { description: detail });
+      toast.error("Create failed", { description: describeError(err) });
     },
   });
 

clients/admin/src/lib/api-client.ts

@@ -5,7 +5,9 @@ export type ApiError = {
   status: number;
   title?: string;
   detail?: string;
-  errors?: Record<string, string[]>;
+  // FluentValidation errors arrive keyed by field (Record); CustomException
+  // (e.g. Identity registration failures) sends a flat string[]. Handle both.
+  errors?: Record<string, string[]> | string[];
   reason?: string;
   [key: string]: unknown;
 };
@@ -21,6 +23,28 @@ export class ApiRequestError extends Error {
   }
 }
 
+/**
+ * Build a user-facing message from an error. When the server includes specific
+ * reasons in the ProblemDetails `errors` extension (validation failures,
+ * Identity errors like "Email is already taken"), those are shown — they tell
+ * the user what to fix. Otherwise falls back to detail / title / message.
+ */
+export function describeError(err: unknown): string {
+  if (err instanceof ApiRequestError) {
+    const raw = err.problem?.errors;
+    const details = Array.isArray(raw)
+      ? raw.filter((e): e is string => typeof e === "string")
+      : raw && typeof raw === "object"
+        ? Object.values(raw)
+            .flat()
+            .filter((e): e is string => typeof e === "string")
+        : [];
+    if (details.length > 0) return details.join(" ");
+    return err.problem?.detail ?? err.problem?.title ?? err.message;
+  }
+  return err instanceof Error ? err.message : String(err);
+}
+
 type RequestInitEx = RequestInit & { skipAuth?: boolean; timeoutMs?: number };
 
 const DEFAULT_TIMEOUT_MS = 30_000;