== Login of an existing user ==

=== Actors ===
User

=== Scenario ===
1. The user clicks on the "LOGIN" button
2. A login form is displayed
3. The user fills out the form and clicks SIGN IN
4. The server validates the form data and checks the Users table
        {{{
        SELECT *
        FROM users
        WHERE username = $username OR email = $username
        LIMIT 1;;
        }}}
5. The user gets a success message and is redirected to the home page