Question: How could I add a link to a page with SignIn via e-mail and then send a verification e-mail? I want to add a user to Wagtail, create group, site with name of the user. Why Wagtail doesn't have a module for that membership site?

Answer: 
I know this post is a bit old but it should be updated. Wagtail makes use of django's in-built auth views.

> 
> Wagtail uses Django’s standard django.contrib.auth.views.LoginView
>  view here, and so the context variables available on the template are
>  as detailed in Django's login view documentation.
> 
> 
> 

<http://docs.wagtail.io/en/v2.6.1/advanced_topics/privacy.html#setting-up-a-login-page>

That said, it should be pretty straight forward. Set up auth as you normally would for a django project, and make your own templates.

<https://docs.djangoproject.com/en/2.2/topics/auth/default/#using-the-django-authentication-system>
Using [Django-registration](https://github.com/macropin/django-registration) is posible as explained here:
[Django-registration setup without password](https://stackoverflow.com/q/5843319/3186190)