API Pull - Update metadata for Coupons and Product after being notified.

[jorgemd24]

Changes proposed in this Pull Request:

Part of #2146

Once the products or coupons are notified, we can still update some metadata as we used to when we were pushing the data. This is particularly useful for coupons, as it allows us to inform the user that the coupon has been sent/notified to Google.

This PR adds the following:

• Once a coupon has been notified, it will update the sync status and sync timestamp.
• A similar approach will be applied to the products.
• I've created a new Interface called HelperNotificationInterface for the ProductHelper and CouponHelper. This is because the AbstractItemNotificationJob expects those classes to have certain methods available. By doing this, we can ensure that those methods are indeed available. The catch is that I had to remove some type hints because PHP versions earlier than 8 don't allow multiple types.

Screenshots:

Detailed test instructions:

Coupons

1. Create a new coupon and set the visibility to Show Coupon on Google.
2. Go to WC -> Status -> Action Scheduler -> search for: gla/jobs/notifications/coupons/process_item
3. After the job is finished and has been successfully notified, check the postmeta of the coupon you created. It should have _wc_gla_sync_status = synced and _wc_gla_synced_at set.

Products

1. Create a new product and set the visibility to Sync and Show.
2. Go to WC -> Status -> Action Scheduler -> search for: gla/jobs/notifications/products/process_item
3. After the job is finished and has been successfully notified, check the postmeta of the product you created. It should have _wc_gla_sync_status = synced and _wc_gla_synced_at set.

Additional details:

Changelog entry

[codecov]

Codecov Report

Attention: Patch coverage is 54.54545% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 63.9%. Comparing base (b41bad3) to head (3c57d12).
Report is 299 commits behind head on feature/google-api-project.

Additional details and impacted files

@@                      Coverage Diff                       @@
##             feature/google-api-project   #2338     +/-   ##
==============================================================
+ Coverage                          63.5%   63.9%   +0.4%     
- Complexity                         4391    4443     +52     
==============================================================
  Files                               468     472      +4     
  Lines                             18555   18739    +184     
==============================================================
+ Hits                              11785   11980    +195     
+ Misses                             6770    6759     -11     

Flag	Coverage Δ
php-unit-tests	63.9% <54.5%> (+0.4%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...Jobs/Notifications/AbstractItemNotificationJob.php	100.0% <100.0%> (ø)
src/Jobs/Notifications/CouponNotificationJob.php	100.0% <100.0%> (ø)
src/Jobs/Notifications/ProductNotificationJob.php	100.0% <100.0%> (ø)
...Jobs/Notifications/HelperNotificationInterface.php	0.0% <0.0%> (ø)
src/Coupon/CouponHelper.php	67.4% <55.6%> (-2.1%)	⬇️
src/Product/ProductHelper.php	92.1% <33.3%> (-4.0%)	⬇️

... and 10 files with indirect coverage changes

[ianlin]

Thanks for the PR. I can see both coupon and product's metadata were updated. LGTM.