Using a GraphQL datasource

[NicolaiSchmid]

Hey,
I have a quick question. You've very well described, how to use gramps data-sources with non-GraphQL, eg REST endpoints and how to wrap them in GraphQL.
But I already have a bunch of GQL Microservices, which I would like to merge together. How would you achieve that?
I tried writing data-sources with apollo-toolses makeRemoteExecutableSchema but that brings me in an async loop where I would have to export the gramps object inside a then function, which I don't like.
Since I didn't find anything useful in the docs, do you have any suggestions, how to merge together my endpoints?
Thank you!