allow a datetime.date object to be used instead of datetime.datetime for isodatetime data

[bendichter]

Motivation

fix NeurodataWithoutBorders/nwb-schema#321

thoughts, @rly ?

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running ruff from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.02 🎉

Comparison is base (6808826) 88.26% compared to head (884a93a) 88.28%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #874      +/-   ##
==========================================
+ Coverage   88.26%   88.28%   +0.02%     
==========================================
  Files          45       45              
  Lines        9242     9242              
  Branches     2641     2641              
==========================================
+ Hits         8157     8159       +2     
+ Misses        766      765       -1     
+ Partials      319      318       -1     

Impacted Files	Coverage Δ
src/hdmf/spec/spec.py	90.86% <ø> (ø)
src/hdmf/build/builders.py	100.00% <100.00%> (ø)
src/hdmf/build/classgenerator.py	94.97% <100.00%> (ø)
src/hdmf/build/objectmapper.py	92.75% <100.00%> (+0.24%)	⬆️
src/hdmf/utils.py	96.41% <100.00%> (ø)
src/hdmf/validate/validator.py	84.10% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[rly]

Looks good to me! Thanks.