feat: add ability to set prefix for OTEL environment variable

[Odonno]

Description

Grafana k6 requires env variable with a K6_ prefix. This change allow developers to add a prefix for every OTEL env variables.

See the list of env variables that can be set for a k6 instance: https://grafana.com/docs/k6/latest/results-output/real-time/opentelemetry/#configuration

Fixes # (issue)

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Is this introducing a breaking change?
      • Yes
        • Link to aspire-docs issue (please use this breaking-change template):
      • No
        • Link to aspire-docs issue (please use this doc-idea template):
  • No

[mitchdenny]

This reads to me like K6 can read the ones we emit:

[mitchdenny]

TBH this seems like something that needs to be fixed on the K6 side. If you wanted to work around an issue with any of the variables that they provide you could look at doing this:

builder.AddProject<Projects.HelloAspire_Web>("webfrontend")
    .WithExternalHttpEndpoints()
    .WithReference(apiService)
    .WaitFor(apiService)
    .WithEnvironment(context => {
        context.EnvironmentVariables["K6_OTEL_SERVICE_NAME"] = context.EnvironmentVariables["OTEL_SERVICE_NAME"];
    });

[Odonno]

This reads to me like K6 can read the ones we emit:

That may be possible. Either way, I am not able to make it work with Podman due to some network issues. I'll assume it should work then.

[Odonno]

TBH this seems like something that needs to be fixed on the K6 side. If you wanted to work around an issue with any of the variables that they provide you could look at doing this:

builder.AddProject<Projects.HelloAspire_Web>("webfrontend")
    .WithExternalHttpEndpoints()
    .WithReference(apiService)
    .WaitFor(apiService)
    .WithEnvironment(context => {
        context.EnvironmentVariables["K6_OTEL_SERVICE_NAME"] = context.EnvironmentVariables["OTEL_SERVICE_NAME"];
    });

Clever solution. Thank you.