Add CurrentProfileIndexModel enum

[chris-ashe]

Description

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.64%. Comparing base (d85e386) to head (5ed57b5).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
process/models/physics/physics.py	33.33%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4451   +/-   ##
=======================================
  Coverage   48.64%   48.64%           
=======================================
  Files         151      151           
  Lines       29677    29682    +5     
=======================================
+ Hits        14436    14440    +4     
- Misses      15241    15242    +1     

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