Remove old price model left overs

_Originally: https://github.com/virge-io/pricelist-frontend/issues/250_

Lot's of places still use the hardcoded fields: Frontend + Backend

KindDetail endpoint will be covered in other ticket #270

A CLI script is needed to convert the last remaining prices: there are still some "PrijsCombi's" that use a hardcoded joint or canna price; only PrijsCombi's that were used were converted.

This is a left over of bug/problems when we deployed the new model; we did some last minute changes in the convert to not harm horeca prices: which led to some "unconverted PrijsCombi's".

So write a script that finds these: and remove the hardcoded field values en replace it with the correct json prices. Probably good to check if noc actual ShopToPrice relation exists for them on the canna card.