title: How to create login with react native and how to validate session
body: <p>I need to create a login feature so the users can access their private data.</p>
  
  <p>I know that I can use asyncstorage to store something like an access token after a successful login.
  But how can I validate that token on every "screen" of my app ?
  How to properly check if the token exists ?</p>
  
  <p>In angular I could use some interceptor to do this job.
  How can I do that with react native ?</p>
  
  <p>Thanks.</p>