Prepopulate a `user` field in a Django admin form

It took me a while to find the solution, which I am posting here:

class ArticleAdmin(admin.ModelAdmin):

    form = ArticleAdminForm

    def get_changeform_initial_data(self, request):
        initial = super().get_changeform_initial_data(request)
        initial['submitted_by'] = request.user
        return initial