feature(h2c): optional certificates for TLS

[cv65kr]

Reason for This PR

In case of h2c there a no need to provide certificates with enabled TLS option

Description of Changes

If TLS is enabled certificates files are optional.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.]
[Reviewer TODO: Verify that these criteria are met. Request changes if not]

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.

[rustatian]

Hey @cv65kr 👋

To use gRPC with H2C, IIRC, we also need to update the DialContext method for the temporal client to use DialH2CContext instead.

[cv65kr]

@rustatian Will take a look, I tested it without that and works as expected

[rustatian]

Just curious, is there a h2c option for the temporal server?

[cv65kr]

for Temporal itself I don't think so, but if you use any ingress like treafik or istio you can enable h2c option for 7233 port

[rustatian]

I'm not quite how this works, since the certificates are required here: https://github.com/cv65kr/roadrunner-temporal/blob/patch-1/tls.go#L55

From what I know, h2c for the http and gRPC is a special handler, it should not be activated by skipping the certs... So, could you please write a test for your change?