Add honeypot fields and minimum fill-out time for sign-up form (#15276)

* Add honeypot fields to limit non-specialized spam

Add two honeypot fields: a fake website input and a fake password confirmation
one. The label/placeholder/aria-label tells not to fill them, and they are
hidden in CSS, so legitimate users should not fall into these.

This should cut down on some non-Mastodon-specific spambots.

* Require a 3 seconds delay before submitting the registration form

* Fix tests

* Move registration form time check to model validation

* Give people a chance to clear the honeypot fields

* Refactor honeypot translation strings

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/views/auth/registrations/new.html.haml

@@ -24,6 +24,9 @@
 
   .fields-group
     = f.input :password_confirmation, wrapper: :with_label, label: t('simple_form.labels.defaults.confirm_password'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.confirm_password'), :autocomplete => 'off' }
+    = f.input :confirm_password, as: :string, wrapper: :with_label, label: t('simple_form.labels.defaults.honeypot', label: t('simple_form.labels.defaults.password')), required: false, input_html: { 'aria-label' => t('simple_form.labels.defaults.honeypot', label: t('simple_form.labels.defaults.password')), :autocomplete => 'off' }
+
+  = f.input :website, as: :url, wrapper: :with_label, label: t('simple_form.labels.defaults.honeypot', label: 'Website'), required: false, input_html: { 'aria-label' => t('simple_form.labels.defaults.honeypot', label: 'Website'), :autocomplete => 'off' }
 
   - if approved_registrations? && !@invite.present?
     .fields-group