Fix: use exceptional copy method for Go standard types

[tiendc]

Why

• Copying time.Time can be simplified with a direct copy
• Copying unique.Handle[T] should be shallow. See deepcopy.Copy does not work well with unique.Handle #48

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.63%. Comparing base (648e96c) to head (5906108).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
+ Coverage   96.57%   96.63%   +0.07%     
==========================================
  Files          11       11              
  Lines        1018     1038      +20     
==========================================
+ Hits          983     1003      +20     
  Misses         25       25              
  Partials       10       10              

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud