React Native Stream Group Chat Tutorial: Add room member

add member in server.js

// server/server.js
app.post("/add-member", async (req, res) => {
  const user_id = req.body.user_id;
  const sample_channel = server_side_client.channel('messaging', 'sample-room1');
  const add_member = await sample_channel.addMembers([user_id]);
  console.log("members: ", add_member);
  res.send('ok');
});