How to generate MongoDB entities with JDL with @DBRef annotation in Jhipster

Question

I'm trying to generate MongoDB entities with jdl-studio and I need to define @DBRef annotation for one entity which is related to another. I couldn't find any information in documentation so I hope you can help me. Let's suppose we have two entities, I need Country to have a field list of Region IDs

entity Region {
   regionName String
}
entity Country {
    countryName String
}