feat(api): add openapi specification

[ReenigneArcher]

Description

This PR will attempt to provide an openapi spec for the Sunshine rest API. I am not an expert on this, but I believe once this is available it will be possible to automatically create SDKs in various languages using an SDK generator (https://openapi.tools/#sdk).

The idea came from https://plexapi.dev/Open-API-Specification which generates SDKs using "Speakeasy". Unfortunately, I don't believe Speakeasy has a generous open source license/option, so other generators may need to be considered. Still, the repo has been a good example, starting with the main spec file - https://github.com/LukeHagar/plex-api-spec/blob/main/src/pms-spec.yaml

Additionally, there are spec generators for various languages, but none seem to be available for c++, understandably, so this is being manually created.

TODO:

• CI, build API docs using redoc, lint, etc. redoc: https://dev.to/heymich/a-guide-to-creating-api-documentation-with-redoc-and-github-pages-4i4a
• see if this even works
  • postman
  • redocly in CLion (not working... probably CORS issue)
  • swagger in CLion (not working... probably CORS issue)
• add all endpoints
• generate version number (and other variables) during build/release
• generate/publish SDKs (possibly in separate repos)
• return properly serialized json (boolean, integer) values (probably not this PR)... then remove "types" directory

Other notes:

• if redoc doesn't work out... standalone linting: https://github.com/stoplightio/spectral

Screenshot

Issues Fixed or Closed

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 10.30%. Comparing base (7f0351d) to head (42a3e9a).

Files with missing lines	Patch %	Lines
src/confighttp.cpp	0.00%	3 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #3540     +/-   ##
=========================================
  Coverage   10.30%   10.30%             
=========================================
  Files          90       90             
  Lines       16130    16130             
  Branches     7655     7655             
=========================================
  Hits         1662     1662             
+ Misses      13911    11918   -1993     
- Partials      557     2550   +1993     

Flag	Coverage Δ
Linux	9.68% <0.00%> (ø)
Windows	10.77% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/confighttp.cpp	0.00% <0.00%> (ø)

... and 32 files with indirect coverage changes

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 New issue
1 New Code Smells (required ≤ 0)

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