Add Source Catalog Model

[bmorris3]

(work in progress)

This PR implements exposes a model class for the output from the Source Catalog Step. The schema is defined in https://github.com/spacetelescope/rad/pull/374, and the step is being developed in https://github.com/spacetelescope/romancal/pull/1102.

The tests will fail until https://github.com/spacetelescope/rad/pull/374 is merged.

Checklist

• [ ] Added entry in CHANGES.rst under the corresponding subsection
• [ ] updated relevant tests
• [ ] updated relevant documentation
• [ ] Passed romancal regression testing on Jenkins / PLWishMaster. Link: https://plwishmaster.stsci.edu:8081/job/RT/job/romancal/XXX/

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (087a60d) 97.56% compared to head (ec24d40) 97.60%.

:exclamation: Current head ec24d40 differs from pull request most recent head a46f649. Consider uploading reports for the commit a46f649 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #317 +/- ## ========================================== + Coverage 97.56% 97.60% +0.04% ========================================== Files 30 31 +1 Lines 2788 2839 +51 ========================================== + Hits 2720 2771 +51 Misses 68 68 ```

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[nden]

Superseded by #331