Inconsistent behaviour when loading nodes via GraphQL

[philippguertler]

There are many different ways to load nodes via GraphQL:

• Single node by UUID
• Multiple nodes by UUID
• All nodes
• Elasticsearch
• Nodes of a schema
• Nodes with a tag
• Via node reference / node reference list
• Other languages of a node

When loading nodes without providing a language and there are nodes which don't have content in the default language, some fetchers filter out the node entirely and some include these nodes, but do not provide any further information bound to the content (language, fields, etc.)

We should make sure that all fetchers behave the same way.