Update schema.js

[sylwit]

If you want to use UUID in a nested object, you have to call explicitly the function v4() or v1()

[emmoistner]

@sylwit
This only generates only one each v4 and v1 uuids which will be reused for every vogels.types.uuid()?

I created a possible solution for nested array defaultFunction invocation which could be useful.
https://github.com/bluebridgedigital/vogels/pull/2/files

[sylwit]

Hi @emmoistner

I think it's related with this other issue I opened #156

Your fix seems good to me