JP-3953: Extrapolate barshadow correction to cover wavelength gaps

[melanieclarke]

Resolves JP-3953

Fix an unintended regression introduced by #9085. The current barshadow reference files do not cover all valid wavelengths for all gratings, so the interpolation for the correction needs to extrapolate to cover the gaps.

Tasks

• request a review from someone specific, to avoid making the maintainers review every PR
• add a build milestone, i.e. Build 12.0 (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)
  • 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

[melanieclarke]

Regression tests running here:
https://github.com/spacetelescope/RegressionTests/actions/runs/14084928772

The MOS spec2 test runs on G235M data, which is one of the affected gratings. Running locally, it looks like one of the 6 extracted slits is impacted by the wavelength gap, so I expect to see change in EXTVER 6 for the output products.

Edit:
Regression tests show expected diffs in the MOS spec2 test, similar diffs in the MOS FS spec2 test (using G395M), and additionally some changes in BARSHADOW extension only, for the MOS moving target test and the MOS master background test.

For these last two, the grating is PRISM, so no wavelength gaps are expected. There are now some extrapolated barshadow values at the edges of the arrays, where valid wavelengths are defined, but there is no reference data -- this has no impact on the science data, which is NaN in those regions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.69%. Comparing base (86af1f2) to head (2af0321).
Report is 741 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9326   +/-   ##
=======================================
  Coverage   74.69%   74.69%           
=======================================
  Files         369      368    -1     
  Lines       37117    37106   -11     
=======================================
- Hits        27723    27717    -6     
+ Misses       9394     9389    -5     

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[melanieclarke]

@tapastro - this will need to go into an rc2 for 1.18.0. I have marked it for Build 11.3.

[tapastro]

LGTM

[tapastro]

@meeseeksdev backport to release/1.18.x

[pllim]

Tada: #9335