Running into some pub limitations supporting this right now, working with pub to enable support.

The issue is that pub transforms can only modify code in the package in which the transformer is being executed, but that for this DI generation, the transformer needs to run from the root of the application. This means that the transformer would not be able to modify any code to add the imports or generated files in any other packages.

I'll work on prototyping this, but it's probably best tackled as a separate change.