Implementing local subgraph?

[DoumanAsh]

This is a bit unclear right now from looking at code base.
But it seems plugin is the way to implement subgraph locally.

I have use case where I need router with ability to invoke one of the subgraphs locally. So it would be like use HTTP service to forward request to one subgraph, but another one would be resolved locally.
So I'm wondering if it is possible to do so, but in this case I'm not sure how to compose supergraph schema for this purpose.
It seems ApolloRouter itself supports custom plugins, but I'm not sure if there is a better way to do it than just plugin?

[DoumanAsh]

I developed sample on how to embed router-core using async-graphql for local subgraph

https://github.com/DoumanAsh/graphql-router-example

This allows users who has own graphql servers embed router and introduce federation without a need for separate binary of router