title: Is there a way to instantiate a new client on server side by firebase cloud function?
body: <p>I am developing an app and trying to implement news feed by getstream.io using react native and firebase. 
  Is there a way to generate user token by using firebase cloud function. If there is, would you please give me a pointer how i can do so? (the snippet of codes in cloud function side and client side would be super helpful..) 
  I have seen similar questions, only to find out no specific tutorial.. any help is appreciated!</p>