Federation + Plugin generated graphql schema code not in SDL

### What happened?

I written a Plugin https://github.com/fasibio/autogql and now activate ferderation feature.

Everything works fine, but the Ferderation Router returns Scalar Time not found.
This Scalar will be extends to the schema at the https://github.com/fasibio/autogql plugin.
So I think by generation the federation plugin generates the sdl schema before plugins was running. And so the plugin generated Graphql Declartion is missing.

I am Right ?

### What did you expect?

Federation SDL includes all Plugin schema code as well.

### Minimal graphql.schema and models to reproduce
Comming Soon...
At the moment you can use https://github.com/fasibio/autogql/tree/main/testservice and active ferderation.

### versions
- `go run github.com/99designs/gqlgen latest`?
- `go go1.20.8`?