title: Rails - Add a security key to Sign up form
body: <p>I want to use a universal security key (a defined string) to my sign up page so that the users who are provided with it can sign up. This is to ensure that those who sign up are the intended people.  </p>
  
  <p>In my user schema, I have a string column "security_key" so that in the sign up page it can accept an input for the security key in my user Sign Up page. I am not sure how to implement this though.</p>