Suggestion Summary

In V1 APIs, it was possible to fetch content properties on multiple pieces of content in one request using expands. In V2, it is only possible to fetch content properties on one piece of content at a time. 

To cut down on the amount of calls needed, a solution could be introducing a set of endpoints that would fetch all content properties for a specified type. For example: "Get content properties for pages" -> could fetch all content properties that correspond to the page type, along with filters to help narrow the response down.

This endpoint should be done for all entity types that support content properties.

We could also add a key filter query param to filter only properties with a given key.