Check for unsupported observable IDs in sigma expressions

[dweindl]

Closes #2561.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.76%. Comparing base (2b05a19) to head (4e85838).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2563      +/-   ##
===========================================
+ Coverage    77.70%   77.76%   +0.06%     
===========================================
  Files          325      325              
  Lines        21857    21861       +4     
  Branches      1473     1473              
===========================================
+ Hits         16983    17000      +17     
+ Misses        4847     4834      -13     
  Partials        27       27              

Flag	Coverage Δ
cpp	73.64% <100.00%> (+0.06%)	⬆️
cpp_python	34.21% <100.00%> (+0.01%)	⬆️
petab	37.09% <100.00%> (+0.01%)	⬆️
python	72.41% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
python/sdist/amici/sbml_import.py	79.56% <100.00%> (+0.08%)	⬆️

... and 4 files with indirect coverage changes