Add tests for recurrence generators

[ish-bindra]

The following limitations to using lunartick for ical rules were discovered:

1. It does not support interval with rules that are monthly and have an interval > 1 (e.g. FREQ=MONTHLY;BYMONTHDAY=17;INTERVAL=2)
2. It does not support fortnightly rules (e.g. FREQ=WEEKLY;BYDAY=TH;INTERVAL=2)
3. It does not support BYMONTHDAY=-1 (https://github.com/ordermentum/lunartick/blob/develop/src/iterator.js#L110 shifts the date by an extra month)
4. It does not support multiple values for BYDAY (e.g. FREQ=WEEKLY;BYDAY=MO,WE,FR)
5. It does not support BYSETPOS parameter (e.g. FREQ=DAILY;BYHOUR=8,18;BYMINUTE=30,0;BYSETPOS=1,4)
6. It does not chronologically sort BY rules (e.g. Values will be different for FREQ=DAILY;BYHOUR=8,18;BYMINUTE=0,30 and FREQ=DAILY;BYHOUR=8,18;BYMINUTE=30,0 - Note the BYMINUTE prop)
7. It does not support -ve BYDAY values (e.g. FREQ=MONTHLY;BYDAY=-2FR)

This PR adds some verification tests related to recurrence generator libraries

• Rules without DTSTART
• Rules with DTSTART
• DST thresholds
• Verify above limitations

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[sugendran]

dev dependency?

[sugendran]

I'm assuming this is interim while we transition

[ish-bindra]

Moved to dev dep.
Yeah, can remove once the solution is prod tested.

[sugendran]

Looks reasonable to me. When you clean up lunartick, what's the leave behind unit tests that confirm rrule is set up and working as expected?

[ish-bindra]

Looks reasonable to me. When you clean up lunartick, what's the leave behind unit tests that confirm rrule is set up and working as expected?

That would be the helpers test file https://github.com/ordermentum/steveo/blob/main/packages/scheduler-sequelize/test/helpers_test.ts#L21