fix: Use dynamic port in Makefile start output

[JohannesMahne]

Summary

• Query the actual port from Docker instead of hardcoding 8080 in make start output
• The displayed URLs now respect ENVOY_PORT overrides in .env.override

Test plan

• Set ENVOY_PORT=8888 in .env.override
• Run make start
• Verify the output shows http://localhost:8888 instead of hardcoded 8080

[JohannesMahne]

Test results

[christos68k]

Note that this will hide any failures (e.g. docker port frontend-proxy) inside the pipeline and continue execution. If more robust error handling is needed, there are multiple options (e.g. use bash and pipefail) but the simplest is to lift this logic outside the Makefile into its own shell script, add error handling there, and call that from the Makefile.

[dmathieu]

This is a change on something that is not elastic-specific. It should be upstreamed to avoid conflicts when merging.

[osullivandonal]

Thanks for the change @JohannesMahne , I agree with @dmathieu here, this repo is a fork of https://github.com/open-telemetry/opentelemetry-demo, if changes are needed to none elastic files its advised to make the change upstream in https://github.com/open-telemetry/opentelemetry-demo.

[JohannesMahne]

100% - thank you for all the replies. I will look into the upstream repo and also #195 (comment).