Add openapi protobuf documentation examples

[bvwells]

Add some examples of openapi protobuf annotations.

[codecov-commenter]

Codecov Report

Merging #1429 into v2 will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##               v2    #1429   +/-   ##
=======================================
  Coverage   58.97%   58.97%           
=======================================
  Files          32       32           
  Lines        3895     3895           
=======================================
  Hits         2297     2297           
  Misses       1344     1344           
  Partials      254      254           

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[johanbrandhorst]

This looks good, with the exception that we need to use the new package name in the annotations. Thanks!

[johanbrandhorst]

Thanks for your contribution!