Convert tweakreg segmentation connectivity to integer

[jdavies-st]

This PR fixes a bug when using the new SourceFinder (via segmentation) starfinder in tweakreg which was added in #8203. ConfigObj option always returns a string, and that causes problems when one wants options that are ints or floats. They need to be specifically cast to the correct type.

Another reason to stop using ConfigObj. ;-)

The bug is the following:

    TweakRegStep.call(files_to_tweak, save_results=True, suffix="cal",
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/stpipe/step.py", line 653, in call
    return instance.run(*args)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/stpipe/step.py", line 479, in run
    step_result = self.process(*args)
                  ^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/jwst/tweakreg/tweakreg_step.py", line 208, in process
    catalog = make_tweakreg_catalog(
              ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/jwst/tweakreg/tweakreg_catalog.py", line 220, in make_tweakreg_catalog
    sources = StarFinder(model.data, threshold, mask=coverage_mask, **starfinder_kwargs)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/jwst/tweakreg/tweakreg_catalog.py", line 56, in _SourceFinderWrapper
    segment_map = finder(data, threshold, mask=mask)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/photutils/segmentation/finder.py", line 191, in __call__
    segment_img = detect_sources(data, threshold, self.npixels, mask=mask,
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/astropy/utils/decorators.py", line 604, in wrapper
    return function(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/photutils/segmentation/detect.py", line 396, in detect_sources
    footprint = _make_binary_structure(data.ndim, connectivity)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdavies/miniconda3/envs/jwst/lib/python3.11/site-packages/photutils/segmentation/utils.py", line 96, in _make_binary_structure
    raise ValueError(f'Invalid connectivity={connectivity}.  '
ValueError: Invalid connectivity=8.  Options are 4 or 8.

One may want to update one of the regtests to use segmentation as the starfinder. 2 other things for comment:

The current starfinder kwarg in spec is fine, but sourcefinder would be better, as most sources in JWST images are not stars, but galaxies. The more general term might be more accurate.

Currently the segmentation method doesn't convolve the image first before running detection. This is done in the standard photutils docs and in SourceCatalogStep, so perhaps this was an oversight and should be added. This is needed to boost S/N of detections.

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.21%. Comparing base (4cc0ac1) to head (61b31fc).
Report is 1 commits behind head on master.

❗ Current head 61b31fc differs from pull request most recent head 07154b3. Consider uploading reports for the commit 07154b3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8309      +/-   ##
==========================================
+ Coverage   75.15%   75.21%   +0.05%     
==========================================
  Files         470      474       +4     
  Lines       38604    38810     +206     
==========================================
+ Hits        29014    29192     +178     
- Misses       9590     9618      +28     

Flag	Coverage Δ		*Carryforward flag
nightly	77.37% <ø> (-0.03%)	⬇️	Carriedforward from 4cc0ac1

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[larrybradley]

Thanks, @jdavies-st

[emolter]

looks good, thanks!

[hbushouse]

Regression test run started at https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/1234

[hbushouse]

Regression test run is clean, as expected. Merging.