Support meeting recurrence/exceptions

[97eighty]

A few tickets open in code4recover/12-step-meeting-guide requesting exceptions in meeting recurrence. Existing spec supports a standard once per week recurrence. Consider adding support for other recurrence types or an exception list that changes the weekly behavior.

Monthly Meeting
code4recovery/12-step-meeting-list#145

Every 2nd Week
code4recovery/12-step-meeting-list#156

We could possibly use the ical spec for exceptions and support a string to identify the exceptions.

[joshreisner]

This is very ambitious, I looked at iCal recurrence and it's very complex! That said, just wanted to give two thoughts:

• you can currently use the meeting guide spec to import to the app with day as an array, eg day: [1, 3],
• meeting guide currently only supports weekly meetings, so if we want to add some logic to make this work we should coordinate it so it works in TSML, TSML UI, and Meeting Guide, and the user interface is super clear and consistent for users