Use Altcha on the human authentication form

[marien-probesys]

Is your feature request related to a problem? Please describe.

For now, the human authentication form provides a honeypot system to prevent bots to validate themselves. This solution could be improved by using a more powerful system, while not being too intrusive for the users.

Describe the solution you'd like

Add https://altcha.org/ on the human authentication form. See the documentation:

• backend: https://altcha.org/docs/v2/server-integration/
• frontend: https://altcha.org/docs/v2/widget-integration/

See also how it is integrated in https://github.com/tito10047/altcha-bundle (but don't use this bundle as I'm sure we don't need a new dependency for this)

Describe alternatives you've considered

N/A

Additional context

Depends on #124