Like the title mentions, I have checked the following resources :
- https://developer.github.com/v3/apps/#create-a-github-app-from-a-manifest
- https://developer.github.com/apps/building-github-apps/creating-github-apps-from-a-manifest/
And it seems that a manual user interaction is required to create the app as it requires redirecting people to GitHub to create a new GitHub App.