feat(mpc): add ping edge function

mpc/edge/supabase/.gitignore

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+# Supabase
+.branches
+.temp
+.env

mpc/edge/supabase/functions/ping/index.ts

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+const resendSecret = Deno.env.get("RESEND_SECRET")
+const resendApiKey = Deno.env.get("RESEND_API_KEY")
+
+const handler = async (request: Request): Promise<Response> => {
+  const { secret, email } = await request.json()
+  if (secret !== resendSecret) {
+    return new Response(JSON.stringify("too bad"), {
+      status: 403,
+      headers: {
+        "Content-Type": "application/json"
+      }
+    })
+  }
+  const res = await fetch("https://api.resend.com/emails", {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/json",
+      Authorization: `Bearer ${resendApiKey}`
+    },
+    body: JSON.stringify({
+      from: "Union Ceremony <[email protected]>",
+      to: [email],
+      reply_to: "[email protected]",
+      subject: "Your Turn Is Almost Here - Log Into Union Ceremony",
+      html: `
+        <p>
+          Your contribution slot for the Union Trusted Setup Ceremony is almost here.
+        </p>
+        <p>
+          Your place in queue: <strong>5</strong><br/>
+          Estimated time until your slot: between <strong>1 hour</strong> and <strong>5 hours</strong>
+        </p>
+        <p>
+          Please go to <strong><a href="https://ceremony.union.build">ceremony.union.build</a></strong>, log in, and follow all steps on the page.<br/>
+          If you do not follow all steps by the time your contribution slot arrives, <strong>you will lose your slot</strong>.
+        </p>
+      `
+    })
+  })
+  const data = await res.json()
+  return new Response(JSON.stringify(data), {
+    status: 200,
+    headers: {
+      "Content-Type": "application/json"
+    }
+  })
+}
+
+Deno.serve(handler)