Expose error code in SendError #97

Job	Run time
Test with Codecov coverage (ubuntu-latest / 1.23)	59s
golangci-lint (1.23)	34s
Dependency review	14s
Go vulnerabilities check	29s
REUSE Compliance Check	18s
Test with SonarQube review (ubuntu-latest / 1.23)	1m 28s
Test on FreeBSD 13.4'	2m 12s
Test on FreeBSD 14.1	2m 15s
Test on FreeBSD 14.0	2m 40s
Test (macos-latest / 1.19)	45s
Test (macos-latest / 1.20)	53s
Test (macos-latest / 1.21)	36s
Test (macos-latest / 1.23)	45s
Test (macos-latest / 1.22)	39s
Test (ubuntu-latest / 1.19)	29s
Test (ubuntu-latest / 1.20)	30s
Test (ubuntu-latest / 1.22)	21s
Test (ubuntu-latest / 1.23)	37s
Test (ubuntu-latest / 1.21)	37s
Test (windows-latest / 1.19)	1m 12s
Test (windows-latest / 1.20)	2m 14s
Test (windows-latest / 1.21)	1m 40s
Test (windows-latest / 1.22)	3m 35s
Test (windows-latest / 1.23)	51s
	26m 53s

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