feat(grpc): add support for authority pseudo-header

[Oursin]

What?

This PR adds support for setting the authority pseudo-header when sending gRPC requests.

Why?

This MR is similar to #3454, which was not accepted because the feature was supposed to work without changes using the dns://authority/endpoint syntax.

The company I work at uses gRPC services with TLS certificates matching the gRPC service name. So for example we would have a gRPC service company.test.v1 hosted on a machine reachable from test-v1.internal.company.com, but exposing a certificate signed for company.test.v1.

I tried using the dns:/// syntax like this:

client.connect('dns://company.test.v1/test-v1.internal.company.com:443', {timeout: '5s', tls: TLSParams});

But I end up with this error, the same as if I was simply trying to connect without the dns:/// syntax.

context deadline exceeded: connection error: desc = "transport: authentication handshake failed: tls: failed to verify certificate: x509: certificate is valid for company.test.v1, not test-v1.internal.company.com

I have a workaround by configuring my /etc/hosts file so that the addess in connect is company.test.v1 but I would prefer if it was a k6 parameter directly.

With the changes made in this MR i can connect like this:

client.connect('test-v1.internal.company.com:443', {timeout: '5s', authority: 'company.test.v1', tls: TLSParams});

Which allows the TLS handshake to work properly.

Checklist

• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added tests for my changes.
• I have run linter and tests locally (make check) and all pass.

Checklist: Documentation (only for k6 maintainers and if relevant)

Please do not merge this PR until the following items are filled out.

• I have added the correct milestone and labels to the PR.
• I have updated the release notes: link
• I have updated or added an issue to the k6-documentation: grafana/k6-docs#NUMBER if applicable
• I have updated or added an issue to the TypeScript definitions: grafana/k6-DefinitelyTyped#NUMBER if applicable

Related PR(s)/Issue(s)

#3454

[CLAassistant]

All committers have signed the CLA.

[codebien]

Hey @Oursin, thanks for taking care of this. 🎉 Much appreciated 🙇 We plan to merge as soon as we get a green CI.

[AgnesToulet]

I've tested it and it works great, thank you for your contribution! 🎉