add vo_mapping function

[dirksammel]

This PR adds a function for mapping a user in the record to a VO. This function can be added to a Field in the config file and uses the return value of the Field as parameter.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.12%. Comparing base (ecd3b28) to head (97e0d65).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1056      +/-   ##
==========================================
+ Coverage   63.02%   63.12%   +0.09%     
==========================================
  Files          49       49              
  Lines        5983     5993      +10     
  Branches       62       65       +3     
==========================================
+ Hits         3771     3783      +12     
+ Misses       2206     2204       -2     
  Partials        6        6              

Components	Coverage Δ
apel_plugin	71.96% <100.00%> (+0.87%)	⬆️
auditor	68.84% <ø> (ø)
auditor_client	94.38% <ø> (ø)
slurm_collector	67.67% <ø> (ø)
slurm_epilog_collector	0.00% <ø> (ø)
htcondor_collector	∅ <ø> (∅)
priority_plugin	37.82% <ø> (ø)