Add newsletter subscription boolean

[RuthShryock]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

Newsletter subscription field for TOS feature

Notes

Added newsletter_subscription boolean to extra_details which reflects whether the user is subscribed to the newsletter.

To test:

• navigate to the create an account page (should see a new field with checkbox to subscribe to the newsletter)
• create a new user who is subscribed to the newsletter
• after confirming the email and signing in, you should see newsletter_subscription: True in the /me endpoint

[notion-workspace]

Add user Boolean that indicates newsletter status

[RuthShryock]

All the tests pass locally, build failure doesn't relate to this code: internal discussion .