Recommend CMS for publishing

We have a team of authors that create/review/collaborate/reject/approve/publish on a data model (we call it a project). This data model has quite a few relationships with other data models but it mostly consists of text (rich text) and resources (images, embedded docs, files, videos) etc. It has a very well defined structure that of course changes from time to time (new fields are being added, new relationships, fields are being dropped, etc). Some key features that we would like to have: - live collaboration on the whole project (while keeping this well defined structure, meaning having specific fields in a form that many people can edit simultaneously) - reviewing process with comments/tasks - role based permissions system - version control, project history, etc - a system similar to Git would be nice to have, meaning an author could branch of a published project and then create some sort of a Merge Request - media library (import from Google or another provider such as Cloudinary) - CDN support - being extensible so we can write code to extend it Are there any recommendations from your experience? Thank you