Fix BC break when using RFC3339 constants with Zulu timezone

[alganet]

Addresses BC break in 2.x series reported in #1442 (maybe too late, but better than never fixed!)

I'm not sure we should do this in 3.x. Doing it in 2.x just to ensure BC with 2.2. While the PHP constant says "RFC3339", the RFC itself has several formats and PHP does not provide a full breadth of constants for all of the specified formats, so it's really not our fault. There should be a \DateTime::RFC3339_Z or something. I'll provide a 3.x follow up in the next few days.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.12%. Comparing base (79f214c) to head (caa13e7).
⚠️ Report is 1 commits behind head on 2.4.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.4    #1593      +/-   ##
============================================
+ Coverage     94.09%   94.12%   +0.02%     
- Complexity      455      459       +4     
============================================
  Files            99       99              
  Lines          1254     1259       +5     
============================================
+ Hits           1180     1185       +5     
  Misses           74       74              

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[Copilot]

Pull request overview

This PR attempts to fix a backward compatibility break introduced in version 2.3 where RFC 3339 timestamps with the Zulu timezone suffix ('Z') are no longer accepted as valid, addressing issue #1442.

Key changes:

• Modified the CanValidateDateTime trait to replace 'Z' suffix with '+00:00' for RFC3339_EXTENDED format validation
• Added test case to verify RFC3339_EXTENDED format accepts timestamps with 'Z' suffix

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
library/Helpers/CanValidateDateTime.php	Adds logic to replace 'Z' timezone suffix with '+00:00' when validating RFC3339_EXTENDED format
tests/unit/Helpers/CanValidateDateTimeTest.php	Adds test case for RFC3339_EXTENDED format with Zulu timezone suffix

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