Add models for wyckoff_positions

[ml-evs]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.25%. Comparing base (e88ddb6) to head (9369a0b).

Files with missing lines	Patch %	Lines
optimade/models/structures.py	45.45%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2427      +/-   ##
==========================================
- Coverage   90.39%   90.25%   -0.14%     
==========================================
  Files          78       78              
  Lines        5110     5121      +11     
==========================================
+ Hits         4619     4622       +3     
- Misses        491      499       +8     

Flag	Coverage Δ
project	90.25% <45.45%> (-0.14%)	⬇️
validator	90.25% <45.45%> (-0.14%)	⬇️

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