feat: Inject OpenAPI deprecations safely

[Skywalkr-dev]

• Updates: openapi.go to parse and cache the 'deprecated' flag from spec
• Updates: metadata.go to inject generic comment tags for deprecated endpoints

Fixes : #4269

[gmlewis]

Also, it looks like a number of useful comments were removed from metadata.go for no apparent reason. Please review and revert the comment removals from this file.

[Skywalkr-dev]

Also, it looks like a number of useful comments were removed from metadata.go for no apparent reason. Please review and revert the comment removals from this file.

Sorry about that, it should look good now I hope.

[gmlewis]

Better, but some lines were still unnecessarily deleted. If you review your changes in the GitHub user interface, you can see what needs to be fixed:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.49%. Comparing base (eb96f3d) to head (fe9369f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4286   +/-   ##
=======================================
  Coverage   97.49%   97.49%           
=======================================
  Files         192      192           
  Lines       19256    19256           
=======================================
  Hits        18774    18774           
  Misses        267      267           
  Partials      215      215           

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[Skywalkr-dev]

Better, but some lines were still unnecessarily deleted. If you review your changes in the GitHub user interface, you can see what needs to be fixed:

yup, the current commit should fix it.
thanks for the review

[gmlewis]

Thank you, @Skywalkr-dev!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @alexandear - @zyfy29 - @Not-Dhananjay-Mishra - @munlicode