Suggest to the users that register via Oauth subscribing to the newsletter

Is your feature request related to a problem? Please describe.
As a user, when I sign up with the form on meta decidim, I am invited to subscribe to the newsletter.

But if I chose to sign up with my decidim profile, at no moment I get the invitation to subscribe.

Describe the solution you'd like
When I choose to sign up via Oauth, I want to have the possibility to subscribe to the newsletter.

It could be added to the permission page.

Additional context

Does this issue could impact on users private data?
Yes, the email should be saved and "subscribing_newsletter" in DB will be updated. 

Funded by
Could be funded by Open Source Politics