Support all ObjSCIP features

[hedtke]

Closes #29

Adds support for all ObjSCIP features.

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[codecov]

Codecov Report

❌ Patch coverage is 95.74468% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.15%. Comparing base (44d6a47) to head (2dd7bf4).

Files with missing lines	Patch %	Lines
source/model_objscip.cpp	89.47%	0 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #44      +/-   ##
==========================================
- Coverage   97.75%   97.15%   -0.61%     
==========================================
  Files          10       11       +1     
  Lines         223      316      +93     
  Branches       64       89      +25     
==========================================
+ Hits          218      307      +89     
  Misses          4        4              
- Partials        1        5       +4     

Files with missing lines	Coverage Δ
include/scippp/model.hpp	98.73% <100.00%> (+2.43%)	⬆️
source/model.cpp	98.01% <100.00%> (+0.06%)	⬆️
source/model_objscip.cpp	89.47% <89.47%> (ø)

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