feat(confidence-engine): establish authenticated product boundary

app/auth/callback/route.js

@@ -0,0 +1,26 @@
+import { createServerClient } from "@supabase/ssr";
+import { NextResponse } from "next/server";
+
+export async function GET(request) {
+  const requestUrl = new URL(request.url);
+  const code = requestUrl.searchParams.get("code");
+  const response = NextResponse.redirect(new URL("/", requestUrl.origin));
+
+  if (code) {
+    const supabase = createServerClient(
+      process.env.NEXT_PUBLIC_SUPABASE_URL,
+      process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY,
+      {
+        cookies: {
+          getAll: () => request.cookies.getAll(),
+          setAll(cookiesToSet) {
+            cookiesToSet.forEach(({ name, value, options }) => response.cookies.set(name, value, options));
+          },
+        },
+      },
+    );
+    await supabase.auth.exchangeCodeForSession(code);
+  }
+
+  return response;
+}