Allow arbitrary function in set_distance

[Datseris]

(and also allow the potential for downstream optimizations)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.68%. Comparing base (593c782) to head (74de15a).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
src/set_distance.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #37      +/-   ##
==========================================
+ Coverage   79.11%   82.68%   +3.57%     
==========================================
  Files           9        9              
  Lines         383      410      +27     
==========================================
+ Hits          303      339      +36     
+ Misses         80       71       -9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.