Allow users to sign up for updates and to register their site on install

Problem/Motivation

We've recently introduced an Open Outreach newsletter and expanded the options for members on openoutreach.org to access and share support, see the announcement.

As well as signing up on the site, it would be useful to allow users to optionally sign up when installing the distro.

Proposed resolution

Add a install task to allow users to sign up for updates.

Remaining tasks

User interface changes

API changes

Data model changes