add back error page

packages/app/src/app/error/page.tsx

@@ -0,0 +1,39 @@
+import Alert from "@codegouvfr/react-dsfr/Alert";
+import { type NextServerPageProps } from "@common/utils/next";
+import { CenteredContainer } from "@design-system";
+import { notFound } from "next/navigation";
+
+import { Footer } from "../Footer";
+import { Header } from "../Header";
+
+const controlledErrors: Record<string, string | { message: string; source: string }> = {
+  AccessDenied: {
+    source: "login",
+    message: "Vous n'êtes pas staff.",
+  },
+};
+
+const ControlledErrorPage = ({ searchParams }: NextServerPageProps<never, "error" | "source">) => {
+  const error = controlledErrors[`${searchParams.error}`];
+  const source = `${searchParams.source}`;
+
+  if (!error) {
+    notFound();
+  }
+
+  const errorMessage = typeof error === "object" ? (source == error.source ? error.message : notFound()) : error;
+
+  return (
+    <>
+      <Header />
+      <main role="main" id="content" className="grow">
+        <CenteredContainer py="6w">
+          <Alert title="Erreur" severity="error" description={errorMessage} />
+        </CenteredContainer>
+      </main>
+      <Footer type="public" />
+    </>
+  );
+};
+
+export default ControlledErrorPage;