To more closely align return value with other date APIs in WC, namely
WC_Data. Includes changing return value to:
1. a WC_DateTime instead of a timestamp when a scheduled occurrence is found
2. null instead of false, similar to the default of WC_Data::set_date_prop()
To take care of instantiating a canonical job queue for use across
all of WooCommerce, and by 3rd party code.
Also use this new API for enqueuing webhooks instead of raw Action
Scheduler APIs.
As a wrapper for Action Scheduler. This implements the WC_Queue_Interface
so it can be used as WC core's job queue. Implementing WC_Queue_Interface
also means this class has more generic and appropriate job queue nomenclature
than Action Scheduler itself. For exsample, it provides a method for
non-delayed jobs, i.e. WC_Queue_Interface::add(), unlike Action Scheduler,
which requires scheduling a job for now(), which while fairly simple, is not
intuitive or immediately obvious to new comers.
This makes it both more clear and convenient to use Action Scheduler
as a simple job queue instead of just a queue for delayed jobs.
Gerhard Potgieter
Brent Shepherd