Write migration guide from CE -> EE

[PeterPetrik]

We are missing migration guide from CE -> EE. Many users start with CE and when they want EE features they like to keep their projects and users on the new instance.

[PeterPetrik]

Who is the best to document it? @fernandinand or @varmar05 ?

I am wondering also if we do not need to develop some migration script (new repo?) to facilitate this ?

[fernandinand]

Code: #2990