CV2-6701: Check newsletter: add limits

[melsawy]

Description

Add controls and limits to the newsletter feature due to new costs:

Add two new fields to Team.settings:

• tipline_newsletter_enabled (boolean, default: false)
• tipline_newsletter_subscribers_limit (number or nil; nil means no limit; default: nil)
• Document how to use these fields in Confluence (Engineering Cookbook)

Add a migration rake task to enable the newsletter feature for:

• Workspaces using it for non-WhatsApp tiplines (still free)
• WhatsApp tiplines explicitly approved/requested by Shalini
• Update the newsletter Sidekiq worker to check whether the feature is enabled for the workspace before sending, and to restrict number of recipients if needed
• On the frontend, hide Newsletter settings when the feature is not enabled

References: CV2-6701

How to test?

Implement unit tests

Checklist

• I have performed a self-review of my code and ensured that it is safe and runnable, that code coverage has not decreased, and that there are no new Code Climate issues. I have also followed Meedan's internal coding guidelines.

[caiosba]

Thanks, Sawy! From my side, the only blocker is the each / find_each thing. Did you test the migration locally? Were you able to cover all 3 cases with the data you have in your local database?

[melsawy]

Thanks, Sawy! From my side, the only blocker is the each / find_each thing. Did you test the migration locally? Were you able to cover all 3 cases with the data you have in your local database?

Yes Caio

[caiosba]

Thanks for addressing the change requests!