RCAL-1392 Refactor public vs private interface

[stscieisenhamer]

Resolves RCAL-1392

This PR clarifies the distinction between the intended public API and private API. Significant change is placing most of the utility code into private modules.

Tasks

• request a review from someone specific, to avoid making the maintainers review every PR
• add a build milestone, i.e. 24Q4_B15 (use the latest build if not sure)
• Does this PR change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see changelog readme for instructions)
    • if your change breaks existing functionality, also add a changes/<PR#>.breaking.rst news fragment
  • update or add relevant tests
  • update relevant docstrings and / or docs/ page
  • start a regression test and include a link to the running job (click here for instructions)
    • Do truth files need to be updated ("okified")?
      • after the reviewer has approved these changes, run okify_regtests to update the truth files
• if a JIRA ticket exists, make sure it is resolved properly

[codecov]

Codecov Report

❌ Patch coverage is 73.26923% with 139 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.71%. Comparing base (97f0385) to head (c4b3c64).

Files with missing lines	Patch %	Lines
romancal/orientation/_pointing.py	31.20%	86 Missing ⚠️
romancal/orientation/_transforms.py	84.04%	26 Missing ⚠️
romancal/orientation/_wcs.py	81.01%	15 Missing ⚠️
romancal/orientation/_lib.py	93.18%	6 Missing ⚠️
romancal/lib/engdb/engdb_edp.py	62.50%	3 Missing ⚠️
romancal/lib/engdb/engdb_mast.py	97.43%	1 Missing ⚠️
romancal/scripts/set_telescope_pointing.py	50.00%	1 Missing ⚠️
romancal/scripts/v1_calculate.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2314      +/-   ##
==========================================
+ Coverage   80.60%   80.71%   +0.10%     
==========================================
  Files         155      159       +4     
  Lines        9409     9436      +27     
==========================================
+ Hits         7584     7616      +32     
+ Misses       1825     1820       -5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[stscieisenhamer]

regression test #1