Make LDB sync never clash with LMB data

[abeforgit]

Overview

We now unfortunately have to deal with 2 sources of truth when it comes to Person data (names in particular). We need to keep ingesting Person instances from the leidinggevenden database, because LMB does not track them, and there are many people which have a Functionaris instance, but no Mandataris instance (they are, after all, different jobs). However, there are some, (I count 31 at the time of the pr), where the same person has held both Functionaris and Mandataris positions throughout their career.

In that case, we have a possible clash of data, if LMB is updated without the corresponding update to LDB.

This pr makes it so that the LDB sync script never enters Person instances we already have from LMB. It only checks the public graph, but I've confirmed there are no instances of private Persons which are not also in the public graph.

As a side, this pr also flat out deletes the MDB sync script, as we really don't want to run that on accident, ever. Should we ever need it again, it's in the git history.

connected issues and PRs:

Setup

How to test/reproduce

Challenges/uncertainties

Checks PR readiness

• UI: works on smaller screen sizes
• UI: feedback for any loading/error states
• Check cancel/go-back flows
• Check database state correct when deleting/updating (especially regarding relationships)
• changelog
• no new deprecations