Enable enhanced documentation

[munrojm]

This PR includes:

• API and tag descriptions can now be passed to API for FastAPI generated documentation
• GetByKey now has a more detailed description
• Model fields to project now explicitly listed in sparse fields query op

[codecov]

Codecov Report

Merging #468 (c4d0932) into main (7eca4d5) will decrease coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #468      +/-   ##
==========================================
- Coverage   88.44%   88.26%   -0.19%     
==========================================
  Files          40       40              
  Lines        2631     2633       +2     
==========================================
- Hits         2327     2324       -3     
- Misses        304      309       +5     

Impacted Files	Coverage Δ
src/maggma/api/query_operator/sparse_fields.py	97.05% <ø> (ø)
src/maggma/api/resource/read_resource.py	98.64% <ø> (ø)
src/maggma/api/API.py	81.39% <100.00%> (+0.90%)	⬆️
src/maggma/stores/mongolike.py	82.19% <0.00%> (-1.90%)	⬇️
src/maggma/core/drone.py	92.42% <0.00%> (ø)

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