Internal ticket: https://2u-internal.atlassian.net/browse/TNL-11077 This adds validations to all new CMS API endpoints via serializers. Validations follow the "strong parameter" concept: https://www.mintbit.com/blog/securing-ruby-on-rails-applications-part-3-use-strong-parameters#:~:text=Strong%20parameters%20are%20a%20feature,parameters%20to%20a%20controller%20action.