ImportBuilder/ImportProvider from command line tool that generates `.idea` and `*.iml` files

We have a custom build system, and currently we have a command line tool that will generate `.idea` and `*.iml` project files from our TARGETS files. I would like to create a simple plugin that will allow users to import TARGETS files the same way that users can import pom.xml files, using the same "import..." dialogue in the UI.

I've been looking at this page for guidance. I figured I would have to implement `AbstractExternalProjectImportBuilder` and/or `AbstractExternalProjectImportProvider`. However, I find it unclear from just the abstract methods on these classes for how I would actually do this.

Am I on the right track? How might I go about implementing this plugin that will allow importing TARGETS files on top of the command line tool? Is there a resource I can refer to that can describe to me in a bit more detail what all of these classes do (e.g. just form the name, and signature, it's not clear to me what the `ProjectImportBuilder.commit` method is supposed to do)?

Thanks