title: How to make a custom Authentication Provider in Symfony 4?
body: <p>I want to make a custom Authentication Provider, but I really don't know how to start, the thing is that we just want to store users's email in database, nothing else. </p>
  
  <p>Every month, a password will change, and that password is used by every user to let them access the site. The login form will so look like:</p>
  
  <ul>
  <li>An email field to store the email in database</li>
  <li>A password field but it's not stored with the user it's just one password for everybody.</li>
  </ul>
  
  <p>I don't know if I must store the same password for each user in database or something else... I want the users be identified as "logged in" by symfony, I know I have to make a custom authentication provider but I don't know how... Thanks for your help.</p>