Consider when to emit database IDs in serialisations

[pahjbo]

In general if an entity is a composition then in a full export of a model, then no database ID is required as the object can only appear as a "child" of the parent - however, in the case of serialising in a API then it is more likely that an efficient API design can
only be achieved if the database ID is emitted.

It would be good to be able to make the serialisation "switchable" between these two scenarios.

[pahjbo]

could use @jsonfilter and different object mapper setups