title: How to provide user login with a username and NOT an email?
body: <p>I'd like to use Firebase for my web app that is for people with dementia in a care home. They do not have email or social network accounts so will need a simple username / password sign up / sign in.</p>
  
  <p>What is the easiest way to do this? From what I can see in the docs I'd have to use a custom auth flow but I do not have an existing auth server.</p>
  
  <p>If I do need ot do this what is the easiest way to provide the token? In Azure there is Functions and AWS has Lambda but I see nothing here is Firebase</p>