{% macro get_subject() %}Invitation to register{% endmacro %}
{% macro get_html_body() %}
Dear {first_name},
We'd like to invite you to register for the following event:
{{ event.title }}
You can register (or decline the invitation) by using this link:
{invitation_link}
{% if session %}
Best regards
{{ session.user.full_name }}
{% endif %}
{% endmacro %}