Warn the user when checking "never" expiry option

[elinorbgr]

The previous site had a warning:

Cocher cette case te permet d'être automatiquement reconnu à ta prochaine connexion depuis cet ordinateur.
Il n'est pas conseillé de cocher la case si cette machine n'est pas strictement personnelle.

Re-add this text (with proper translation) as a message (formatted as a bootstrap warning for example) that is hidden unless the user checks the "never" expiry option at login.

[tizot]

I looked for a minimal solution to this issue but I don't see how to dynamically display the message otherwise than by writing a custom template for the login form.
Shall I go for this solution ?

[elinorbgr]

We already have a custom template, at xorgauth/templates/registration/login.html, so if you need to adapt it, go for it 👍