Add coverage command for showing coverage for paths/operations of OpenAPI spec and methods of protocol buffers.

[k1LoW]

SSIA

[github-actions]

Code Metrics Report

	main (993f686)	#625 (f34d6c1)	+/-
Coverage	69.8%	69.9%	+0.1%
Code to Test Ratio	1:0.7	1:0.7	-0.0
Test Execution Time	3m41s	2m53s	-48s

Details

  |                     | main (993f686) | #625 (f34d6c1) |  +/-  |
  |---------------------|----------------|----------------|-------|
+ | Coverage            |          69.8% |          69.9% | +0.1% |
  |   Files             |             50 |             51 |    +1 |
  |   Lines             |           5408 |           5507 |   +99 |
+ |   Covered           |           3777 |           3849 |   +72 |
- | Code to Test Ratio  |          1:0.7 |          1:0.7 |  -0.0 |
  |   Code              |          10778 |          11076 |  +298 |
+ |   Test              |           7649 |           7696 |   +47 |
+ | Test Execution Time |          3m41s |          2m53s |  -48s |

Code coverage of files in pull request scope (74.9% → 74.8%)

Files	Coverage	+/-
book.go	72.3%	-0.1%
coverage.go	67.5%	+67.5%
grpc.go	71.7%	+3.5%
operator.go	78.2%	-1.4%

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Reported by octocov