fix: Fix 'lans' attribute for DataPlatform clusters

What does this fix or implement?

Fixes the first point presented here: https://github.com/ionos-cloud/terraform-provider-ionoscloud/issues/552.

Before this fix, if the lans wasn't present in the tf file, lans: nil would be send in the request, same for routes.

This led to a validation error since the API accepts lans: null only on PATCH requests, routes: null is not accepted at all. The error looks like this:

│ Error: an error occured  while creating a Dataplatform Cluster: 422 Unprocessable Entity: {"httpStatus":422,"messages":[{"errorCode":"dsaas-400","message":"'Value is not nullable' caused by field /properties/lans"}]}

I modified the code and now, if the lans or routes are missing, instead of nil we send an empty list in the body request.

Checklist

[x] PR name added as appropriate (e.g. feat:/fix:/doc:/test:/refactor:)
[ ] Tests added or updated
[ ] Documentation updated
[x] Changelog updated and version incremented (label: upcoming release)
[ ] Github Issue linked if any
[ ] Jira task updated

ionos-cloud / terraform-provider-ionoscloud

fix: Fix 'lans' attribute for DataPlatform clusters #553

What does this fix or implement?

Checklist

Quality Gate passed