feat(auth): request secure messenger start sessions

app/composables/useMessengerStart.ts

@@ -0,0 +1,49 @@
+import { buildMessengerBotStartUrl } from '~/composables/useMessengerBotLink';
+
+type MessengerChannel = 'TELEGRAM' | 'MAX';
+
+type MessengerStartResponse = {
+  ok: true;
+  startToken: string;
+  expiresAt: string;
+  mode: 'login' | 'connect';
+};
+
+type MessengerStartInput = {
+  channel: MessengerChannel;
+  baseUrl: string;
+  email?: string;
+};
+
+export function useMessengerStart() {
+  const pendingChannel = ref<MessengerChannel | null>(null);
+
+  async function openMessengerBot({ channel, baseUrl, email }: MessengerStartInput) {
+    pendingChannel.value = channel;
+
+    const payloadPromise = $fetch<MessengerStartResponse>('/api/auth/messenger-start', {
+      method: 'POST',
+      body: {
+        channel,
+        email,
+      },
+    });
+    payloadPromise.finally(() => {
+      pendingChannel.value = null;
+    });
+
+    const payload = await payloadPromise;
+
+    const startUrl = buildMessengerBotStartUrl(baseUrl, payload.startToken);
+    if (import.meta.client) {
+      window.open(startUrl, '_blank', 'noopener,noreferrer');
+    }
+
+    return payload;
+  }
+
+  return {
+    pendingChannel,
+    openMessengerBot,
+  };
+}