Resolve zaaktype and resultaat [Backend]

[SilviaAmAm]

In the old version of the app, the following fields were shown on the destruction list creation page:

• looptijd = einddatum - startdatum (in days, and if no eindatum present, use today())
• resultaattype => nested binnen resultaat (dus deze moet ook resolved worden)
• bewaartermijn = zaak.resultaat.resultaattype.archiefactietermijn
• vcs = zaak.zaaktype.processtype.nummer
• relaties => 'yes' if len(zaak.relevanteAndereZaken), else 'no'

To be able to show these fields, use the zaaktype and the resultaat type should be JSON fields instead of URL Fields.