Change package name
If the user did not give a package id, ask for it. It must look like com.company.app (dot-separated, no spaces).
Then from the project root:
flutter pub run change_app_package_name:main {package.id}
Example: flutter pub run change_app_package_name:main com.new.package.name
Done when the command exits 0. Report the package id that was applied.