Ivoa compliant units

[mairanteodoro]

Resolves RCAL-nnnn

Closes #

This PR addresses ...

Tasks

• Update or add relevant roman_datamodels tests.
• Update relevant docstrings and / or docs/ page.
• Does this PR change any API used downstream? (If not, label with no-changelog-entry-needed.)
  • Write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types).
  • Start a romancal regression test (https://github.com/spacetelescope/RegressionTests/actions/workflows/romancal.yml) with this branch installed ("git+https://github.com/<fork>/rad@<branch>").

News fragment change types:

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

❌ Patch coverage is 99.29078% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.28%. Comparing base (087a60d) to head (3033a31).
⚠️ Report is 233 commits behind head on main.

Files with missing lines	Patch %	Lines
src/roman_datamodels/datamodels/_core.py	75.00%	1 Missing ⚠️
src/roman_datamodels/datamodels/_utils.py	97.77%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #625      +/-   ##
==========================================
- Coverage   97.56%   95.28%   -2.28%     
==========================================
  Files          30       27       -3     
  Lines        2788     2949     +161     
==========================================
+ Hits         2720     2810      +90     
- Misses         68      139      +71     

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