{# In auth.login.providers and signup.providers. GitHub's dark grey comes
   from assets/css/github.css (.btn-github), so the button looks like
   GitHub's in any shell. #}
<a href="{{ url_for('github.login', next=next_url) if next_url else url_for('github.login') }}"
class="btn btn-github d-flex align-items-center">
    GitHub
</a>