Block disposable email in Supabase

The code

// supabase/functions/before-user-created/index.ts
import { Webhook } from "https://esm.sh/standardwebhooks@1.0.0";

const PIISEND_URL = "https://api.piisend.com/api/v1/intelligence/email";

async function isDisposable(email: string): Promise<boolean> {
  try {
    const r = await fetch(PIISEND_URL, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${Deno.env.get("PIISEND_API_KEY")}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({ email }),
    });
    if (!r.ok) return false;
    const data = await r.json();
    return data.signals?.disposable === true;
  } catch {
    return false;
  }
}

Deno.serve(async (req) => {
  const payload = await req.text();
  const headers = Object.fromEntries(req.headers);
  const wh = new Webhook(Deno.env.get("SUPABASE_AUTH_HOOK_SECRET")!);
  const { user } = wh.verify(payload, headers) as { user: { email?: string } };

  if (user.email && await isDisposable(user.email)) {
    return new Response(
      JSON.stringify({ error: { message: "Please use a permanent email address.", http_code: 400 } }),
      { status: 400 },
    );
  }

  return new Response(JSON.stringify({}), { status: 200 });
});