Use route handler instead of page for SSO

src/app/sso/route.tsx

@@ -0,0 +1,31 @@
+import { getForumSso } from "@olinfo/training-api";
+import { redirect } from "next/navigation";
+import { type NextRequest, NextResponse } from "next/server";
+
+export async function GET(request: NextRequest) {
+  const token = request.cookies.get("training_token")?.value;
+
+  // User is logged out.
+  if (token === undefined) {
+    const redirectUrl = request.nextUrl.pathname + request.nextUrl.search;
+    redirect(`/login?redirect=${encodeURIComponent(redirectUrl)}`);
+  }
+
+  const payload = request.nextUrl.searchParams.get("sso");
+  const signature = request.nextUrl.searchParams.get("sig");
+
+  if (payload === null || signature === null) {
+    return NextResponse.json(
+      { message: "Parameters sso and sig must be provided." },
+      { status: 400 },
+    );
+  }
+
+  const { return_sso_url: returnSsoUrl, parameters } = await getForumSso(
+    payload,
+    signature,
+    `training_token=${token}`,
+  );
+
+  redirect(`${returnSsoUrl}?${parameters}`);
+}