Graphql Service Query

It will add another 10ms overhead or so, but nothing that big.

Here are a few tests that run with each commit: https://github.com/Squidex/squidex/blob/master/backend/tools/TestSuite/TestSuite.ApiTests/ContentQueryTests.cs#L380

You can use the client library from nuget for that.

Let me try to go this way but I would still like to do it from within the code. If you have an opinion on this subject and can help, I would still like to consider it.