feat: add index.ts files for models, schemas, and services

[jordanshatford]

closes: #136

NOTE: see each commit (as I added more snapshot tests for clients generated with a name ApiClient)

[codecov]

Codecov Report

Attention: Patch coverage is 90.47619% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 90.67%. Comparing base (e65f07c) to head (5c58417).

Files	Patch %	Lines
src/utils/write/models.ts	75.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
+ Coverage   89.69%   90.67%   +0.97%     
==========================================
  Files          74       75       +1     
  Lines        3941     3945       +4     
  Branches      469      475       +6     
==========================================
+ Hits         3535     3577      +42     
+ Misses        404      366      -38     
  Partials        2        2              

Flag	Coverage Δ
unittests	90.67% <90.47%> (+0.97%)	⬆️

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