feat: support setup guide for admin

app/api/setup/route.ts

@@ -0,0 +1,31 @@
+import { redirect } from "next/navigation";
+
+import {
+  checkUserStatus,
+  getAllUsersCount,
+  setFirstUserAsAdmin,
+} from "@/lib/dto/user";
+import { getCurrentUser } from "@/lib/session";
+
+export async function GET(req: Request) {
+  try {
+    const user = checkUserStatus(await getCurrentUser());
+    if (user instanceof Response) return user;
+
+    const count = await getAllUsersCount();
+
+    if (count === 1 && user.role === "USER") {
+      const res = await setFirstUserAsAdmin(user.id);
+      if (res) {
+        return Response.json({ admin: res.role === "ADMIN" }, { status: 201 });
+      }
+      return Response.json({ admin: false }, { status: 400 });
+    }
+
+    return redirect("/admin");
+  } catch (error) {
+    return Response.json(error?.statusText || error, {
+      status: error.status || 500,
+    });
+  }
+}