Inconsistency between how fields can be specified for GET and form-data POST requests

[theosanderson]

For GET requests you can make a request:

https://lapis-main.loculus.org/cchf/sample/details?fields=accession,accessionVersion

However the corresponding POST request, which is what the Swagger UI generates, doesn't work:

curl -X 'POST' \
  'https://lapis-main.loculus.org/cchf/sample/details' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  -d 'fields=accession,accessionVersion'`

But one can work around this with:

curl -X 'POST' \
  'https://lapis-main.loculus.org/cchf/sample/details' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  -d 'fields=accession&fields=accessionVersion'