Documents are the root objects for a request body (post, patch) or response body (Dogado\JsonApi\Model\Document\DocumentInterface).
A document contains "data" (collection of resources) and can contain meta information, errors, links and related resources ("includes").
The document serializer (a class implementing Dogado\JsonApi\Serializer\DocumentSerializerInterface) is responsible for turning
document objects (and their resources) into a php array in JSON API structure which can be JSON encoded and returned as response.
The default serializer should be a good choice, but it's also possible to use a custom serializer.
The default serializer will remove empty "data" if "errors" or "meta" is available. It will also remove empty data in
relationship if "meta" or "links" is available for a relationship.
If empty data should be retained, the default serializer offers the option keepEmptyData as first constructor argument.
The document deserializer (a class implementing Dogado\JsonApi\Serializer\DocumentDeserializerInterface) is responsible
for turning php arrays into document objects (and their resources).
The default deserializer should be a good choice, but it's also possible to use a custom deserializer.