fix: human-readable timestamp of sent newsletters

[dkoo]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Fixes a bug where the human-readable timestamp shown next to sent newsletters doesn't respect the site's local timezone.

How to test the changes in this Pull Request:

1. Ensure your site has a time zone set in Settings > General that's different from GMT/Universal Time.
2. On trunk, send a newsletter.
3. Go back to the Newsletters post list and observe that the sent label says something inaccurate. For instance, my site is set to Denver/Mountain Time, and so seconds after sending the newsletter the human-readable timestamp reads like this:

4. Check out this branch and refresh. Confirm that the timestamp is now more accurate based on when the newsletter was actually sent:

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

---

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[miguelpeixe]

Works well after the suggested tweak!

[miguelpeixe]

Not sure why tests started failing now 🤔

[dkoo]

Not sure why tests started failing now 🤔

It's because $sent could have been false if the post didn't have the newsletter_sent meta. 442c522 should fix this by explicitly checking for publish or private post status. Also, even if a post already has the newsletter_sent meta, it could be the wrong date, so we want to overwrite it in that case if it doesn't equal the actual publish date timestamp.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 17.71%. Comparing base (25ecc21) to head (442c522).
Report is 37 commits behind head on trunk.

Files	Patch %	Lines
includes/class-newspack-newsletters.php	75.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk    #1590      +/-   ##
============================================
+ Coverage     17.69%   17.71%   +0.02%     
- Complexity     2327     2330       +3     
============================================
  Files            43       43              
  Lines          8784     8784              
============================================
+ Hits           1554     1556       +2     
+ Misses         7230     7228       -2     

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[matticbot]

🎉 This PR is included in version 3.1.0-alpha.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[matticbot]

🎉 This PR is included in version 3.1.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀