Add support for subsystems

[daniel-thom]

No description provided.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (0ac534a) 78.83% compared to head (f27660f) 79.54%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #325      +/-   ##
==========================================
+ Coverage   78.83%   79.54%   +0.70%     
==========================================
  Files          52       53       +1     
  Lines        4135     4218      +83     
==========================================
+ Hits         3260     3355      +95     
+ Misses        875      863      -12     

Flag	Coverage Δ
unittests	79.54% <97.34%> (+0.70%)	⬆️

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

Files	Coverage Δ
src/InfrastructureSystems.jl	80.00% <ø> (ø)
src/component.jl	94.67% <ø> (-0.60%)	⬇️
src/components.jl	90.00% <100.00%> (+0.15%)	⬆️
src/subsystems.jl	100.00% <100.00%> (ø)
src/supplemental_attributes.jl	93.58% <100.00%> (+0.16%)	⬆️
src/supplemental_attributes_container.jl	90.00% <100.00%> (+0.52%)	⬆️
src/iterators.jl	97.29% <96.87%> (-2.71%)	⬇️
src/system_data.jl	90.99% <90.00%> (+1.28%)	⬆️

... and 1 file with indirect coverage changes

[jd-lara]

These changes look good to me. We probably need to start with the implementation in PowerSimulationsDecomposition to find if there will be more requirements. This PR is sufficient for integration into PSY