Endpoint updates

[munrojm]

This PR contains:

• Update MPRester with more explicit methods and tests
• Overhaul phonon endpoint
• Disable appropriate tests when no API key in environment
• Enable bare Monty encoded response for most endpoints

[codecov-commenter]

Codecov Report

Merging #326 (c278b23) into main (428f1dd) will increase coverage by 0.35%.
The diff coverage is 95.65%.

@@            Coverage Diff             @@
##             main     #326      +/-   ##
==========================================
+ Coverage   89.09%   89.45%   +0.35%     
==========================================
  Files          59       59              
  Lines        1917     1916       -1     
==========================================
+ Hits         1708     1714       +6     
+ Misses        209      202       -7     

Impacted Files	Coverage Δ
src/mp_api/routes/charge_density/client.py	94.11% <83.33%> (-2.32%)	⬇️
src/mp_api/matproj.py	97.58% <100.00%> (+3.87%)	⬆️
src/mp_api/routes/__init__.py	100.00% <100.00%> (ø)
src/mp_api/routes/phonon/client.py	100.00% <100.00%> (ø)
src/mp_api/routes/phonon/query_operators.py	0.00% <0.00%> (-100.00%)	⬇️
src/mp_api/routes/electrodes/client.py	91.66% <0.00%> (+4.16%)	⬆️
src/mp_api/routes/materials/utils.py	100.00% <0.00%> (+25.71%)	⬆️

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