extract DBML code

[Felienne]

WIP for automatic database schema generation for documentation purposes (#4678)

The code we generate, creates this:

https://dbdiagram.io/d/Hedy-Database-665897b8b65d9338791bcce4

For now I am manually copying but ultimately we might directly ping the dbdiagram api and have a live version?

Still working on creating the relationships, but I think I need some input from @rix0rrr for that.