title: Simple user registration with Amazon Cognito
body: <p>In the course of building an android application I've run into the heavy issue of user management. </p>
  
  <p>I see all over the place services that allow for users to register in my app using google, facebook, amazon, twitter, etc. (Amazon Cognito, Janrain, Google Identity Toolkit).</p>
  
  <p>Ideally I would like to make use of Amazon Web Services throughout my application and, thusly, would need to make use of Amazon Cognito. However, as far as I can tell Cognito only provides for simple user registration via Facebook, Amazon, and Google, with the added ability to merge with developer authenticated identities. </p>
  
  <p>After multiple hours of research into developing my own identity provider structure, implementing authentication protocols and all that jazz, I've come to the conclusion I have no idea what I'm doing in that area and I'd be best served leaving it alone for now.</p>
  
  <p>All I want is to allow users to register to use my app with an email, username, and password, with the option to merge with their social accounts later, via Amazon Cognito. I just can't seem to find any straightforward answers anywhere.</p>
  
  <p>So, how can I create a simple user registration flow that creates users which can later be linked to their other social accounts via Amazon Cognito?</p>