feat: expose http response headers in ServerError

[karel-rehor]

Proposed Changes

• Add http.Header to ServerError
• Add tests of this change
• Add examples of accessing response headers on write fail.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• Tests pass
• Commit messages are conventional
• Sign CLA (if not already signed)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.28%. Comparing base (ece5518) to head (b3c49c7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #100      +/-   ##
==========================================
+ Coverage   85.25%   85.28%   +0.02%     
==========================================
  Files          14       14              
  Lines        1119     1121       +2     
==========================================
+ Hits          954      956       +2     
  Misses        137      137              
  Partials       28       28              

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[alespour]

I think it is safe to assume a correct pointer to As is passed since it's declared just before it, I would just make sure it's the correct target type, ie.

Suggested change

	assert.NotPanics(t, func() {
	errors.As(err, &serr)
	})
	require.True(t, errors.As(err, &serr))

And check return value of errors.As in examples too.

[karel-rehor]

Changed, however linter wants to enforce this solution:

require.ErrorAs(t, err, &serr)

So, used the linter suggestion.

[alespour]

LGTM now.

[bednar]

LGTM 🚀