[FEATURE] Support non-standard character for cron expressions (e.g. L and W character)

[Phumix]

Is your feature request related to a problem? Please describe. When setting up cron scheduler with special character L to make the cron run on example last sunday of month it wont work on Pipedream as Pipedream doesn't support special characters that are non-standard.

Describe the solution you'd like Possibility to use L and W character in cron expressions, so example this cron expression would work: 0 6 * * 7L (At 06:00 AM, on the last Sunday of the month). Can validate cron here: https://crontab.cronhub.io/

Do you have a workaround? date-fns has been suggested here: https://pipedream.com/community/t/how-can-i-make-cron-run-on-the-last-sunday-of-the-month/1847/4 Haven't tested yet.

Comparable features in other tools? https://www.easycron.com/ (Seems to work here)

Additional context Can validate cron expressions here, L and W works: https://crontab.cronhub.io/

For reference: https://help.sumologic.com/03Send-Data/Sources/01Sources-for-Installed-Collectors/Script-Source/Cron-Examples-and-Reference

[crutch12]

bump

[crutch12]

https://github.com/harrisiirak/cron-parser supports it Interface shows correct result, but "Save and continue" fails with "Cron Invalid cron expression for $.interface.timer"

[crutch12]

Also available here: https://pipedream.com/community/t/how-can-i-make-cron-run-on-the-last-sunday-of-the-month/1847

[dylburger]

There are other cases here where the package we use for parsing cron expressions in the frontend differs from the backend implementation, so the schedule ends up being different from the schedule displayed in the frontend. We should correct.

[arinhouck]

I am experiencing a similar issue, my cron ran on 2023-01-04 (Wednesday) and 2023-01-05 (Thursday). I believe it will continue to run through the "day window".