Calendly, but for Ongoing Weekly Meetings?

Looking for a way to easily schedule volunteers for ongoing/recurring group weekly meetings that is integrated with google cal. Calendly only works for on-off meetings. Basically, what I want to do is for a volunteer to be able to schedule a weekly shift (or even better multiple weekly shifts), and then automatically get a google cal invite for a weekly, recurring meeting. And I want the system to only take 50 people per shift. Any thoughts is an easy to use platform like this exists - or if we have to do something custom? Thanks!