API aggregator doesn't add items, it overwrites them

result = { level: list() for level in Visibility }

for item in data:
        result[Visibility(item.visibility)] = item.serialize()

should be

result = { level: list() for level in Visibility }

for item in data:
        result[Visibility(item.visibility)].append(item.serialize())

If not, the lists made in the first line will be overwritten by the serialized content.

oslokommune / devportal-harvest-poc