Handle DbRef in Mongo

[hantsy]

Mongo drivers itself can handle the dbref case.

{
  'title': 'test title', 
  'comments': [ uuid-1, 2, 3] //ref to comment document
}

we can add and remove comment from Post.comments node directly.

[otaviojava]

Hey @hantsy I hope that you're okay.

Once it is a particular behavior, I'll move it to an extension: https://github.com/eclipse/jnosql-mapping-extension/tree/main/jnosql-mongodb-extension

The goal of the NoSQL API is to use the commons behavior, anything else, move to extension.