Write the invite once. It is reused for every Viber group and every email.
Placeholders: {event_title} {event_date} {location} {rsvp_link} (required) {name} (person's name in email, “everyone” in Viber) {group} (Viber group name).
{event_title}
{event_date}
{location}
{rsvp_link}
{name}
{group}
