Add provider for Entity Framework 7
Its very important to have ORM (ODM) support for DDD(Domain Driven Design)-style architectures. DDD is what makes DocumentDB most useful IMHO. Since EF7 was refactored to be extensible and support non-relational databases, I think its important to provide DocumentDB support for EF. This also should make migration of existing EF-based applications to DocumentDB much easier and will attract much more developers to this product.
This feature is now in preview for EF Core 2.2. To learn more, read the blog post and try here, https://blogs.msdn.microsoft.com/dotnet/2018/09/12/announcing-entity-framework-core-2-2-preview-2/
Yes this really useful to have migrating existing EF based application and also vice versa. Now it is hard to do for big application and can't estimate exact estimation efforts to do so.