fix: removing empty meta and link fields if data is empty to match jsonapi-serializer behaviour

[mylescc]

What is the current behavior?

Currently in the rendered, if it's a collection but there aren't any resources, the meta and links fields are returned in the json, even if they are nil. However, if there are more than one resource, the links and meta data fields will be remove if they are nil.

What is the new behavior?

Now we'll be removing any links or meta fields from the json if they are nil, if there aren't any resources. This matches how the serializer in jsonapi-serializer work so it's keeping behaviour consistent.

Checklist

Please make sure the following requirements are complete:

• [x] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been reviewed and added / updated if needed (for bug fixes / features)
• [x] All automated checks pass (CI/CD)