Send User-Agent header with commit hash

[vegarsti]

This PR adds a User-Agent header on the format node-indexer/<hash>. We try follow the convention described on Wikipedia.

This will be very useful when debugging!

We inject the Git hash using option 1 from Adam's excellent resource https://developers.redhat.com/articles/2022/11/14/3-ways-embed-commit-hash-go-programs#1__using__ldflags. Option 3 doesn't work because even when building with -buildvcs, a go build <file> doesn't embed the VCS info, as tracked in this open issue: golang/go#51279 (comment)

Have verified this locally using Docker build.

[vegarsti]

• Send User-Agent header with commit hash #56 👈
• main

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[adammilnesmith]

Option 3 just missing -buildvcs i think

[adammilnesmith]

If you do end up getting runtime/debug ReadBuildInfo() to work then I think we'd probably be interested in the following when debugging on behalf of customers (in priority order if we don't want to squeeze them all in):

• vcs.revision
• GoVersion
• GOARCH
• GOOS
• vcs.modified
• vcs.time

[vegarsti]

Turns out buildvcs doesn't do it for us either 😕 Not when building by listing Go files directly, like we do with go build ... cmd/main.go golang/go#51279 (comment)