register method
Implementation
AFCoreLibraryExtensionContext? register(AFLibraryID id) {
// this can occur when both an app, and a library the app loads, load some third library.
if(libraries.containsKey(id)) {
return null;
}
final context = AFCoreLibraryExtensionContext(id: id, app: this);
libraries[id] = context;
return context;
}