fix: Hook methods should have default non-abstract implementations

[federicobond]

This PR

Fixes Hook methods incorrectly marked as abstract. The Hook class provides default implementations of all hook lifecycle methods. Hook subclasses only need to override the methods they are interested in.

[codecov[bot]]

Codecov Report

Merging #216 (7c264ab) into main (84af1ae) will decrease coverage by 0.08%. The diff coverage is 83.33%.

@@            Coverage Diff             @@
##             main     #216      +/-   ##
==========================================
- Coverage   93.34%   93.27%   -0.08%     
==========================================
  Files          16       16              
  Lines         451      446       -5     
==========================================
- Hits          421      416       -5     
  Misses         30       30              

Flag	Coverage Δ
unittests	93.27% <83.33%> (-0.08%)	:arrow_down:

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Files	Coverage Δ
openfeature/evaluation_context.py	91.66% <100.00%> (+0.75%)	:arrow_up:
openfeature/hook/__init__.py	83.33% <50.00%> (-2.78%)	:arrow_down:

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[federicobond]

@beeme1mr the return None change is just to comply explicitly with the declared return type of the method. It does not introduce any behavior changes and is functionally identical to the previous code.