feat(client): provide a way to select interfaces fields

[AlixBa]

Closes #237

[AlixBa]

@ghostdogpr is the 2nd commit close enough to what you had in mind for #237?

[ghostdogpr]

@AlixBa what I was thinking is a little different. Let's say that for each subtype you want to get the common fields from the interface, plus an extra field for one of the subtypes. To do that, you have to repeat the interface fields for each subtypes. So I was thinking about adding an extra parameter to the option function, that takes an optional SelectionBuilder of the interface. That way, for my example, you only need to pass this one and the SelectionBuilder for the subtype that needs an extra field. Does that make sense?

By the way I merged your other PR, so you can rebase to get rid of the conflicts.

[ghostdogpr]

Ah sorry, what I suggested doesn't work 😆

def parentOption[A](
  onParent: Option[SelectionBuilder[Parent, A] = None,
  onSubType1: Option[SelectionBuilder[SubType1, A]] = None,
  onSubType2: Option[SelectionBuilder[SubType2, A]] = None
)

There is no way to merge the 2 A from the interface and the subtype.

So I think what you did is good. In my example, we can combine parentInterface and parentOption with ~ to select the common fields and the subtype ones. It would be nice to include a test for that.

[AlixBa]

@ghostdogpr I've added one. Not sure it is the right place/what you were expecting though ^^

[ghostdogpr]

Yep, that's good! Thanks!