JP-3305: New association candidate type to group mosaic tiles across targets

[tapastro]

Resolves JP-3305

Closes #7725

This PR addresses a failure to generate associations for MOSAIC association candidates, due to our level 3 imaging candidates requiring a match on target id. This PR introduces a MOSAIC-candidate-specific class that relaxes the target id constraint, utilizing the filler t000 identifier introduced by #8528.

Tasks

• request a review from someone specific, to avoid making the maintainers review every PR
• add a build milestone, i.e. Build 11.3 (use the latest build if not sure)
• Does this PR change user-facing code / API?
  • add an entry to CHANGES.rst within the relevant release section (otherwise add the no-changelog-entry-needed label to this PR)
  • 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

All modified and coverable lines are covered by tests ✅

Project coverage is 61.77%. Comparing base (da9691d) to head (7a7f4a4).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8798      +/-   ##
==========================================
+ Coverage   61.75%   61.77%   +0.02%     
==========================================
  Files         377      377              
  Lines       38750    38777      +27     
==========================================
+ Hits        23931    23956      +25     
- Misses      14819    14821       +2     

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[tapastro]

Regtest run on associations tests ran here: https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/1725/

I okify'ed prematurely, only to get the files into the truth directory. The value/correctness of the association file will have to be determined independent of a test result here, but the associations utilizing the new rule show t000 in the product name, indicating multiple targets are present. They also contain all members matching the optical path, but across all observations linked with the c1000 candidate tag.

[melanieclarke]

LGTM, from a code and documentation perspective.

[tapastro]

Started a test run against only sdp_pools here: https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/1732/