Fix empty response from server when running curl on music demo app

[pantrif]

This allows curling the music demo app outside of the running container.

[ghost]

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[ableegoldman]

@pantrif Hi! You submitted this PR fairly soon after we merged (we think) a fix for this issue, where we changed KAFKA_MUSIC_APP_REST_HOST from localhost to 0.0.0.0. I just want to confirm, were you hitting this issue before or also after we made the above change?

ie did you test the demo app with host 0.0.00 or was it still localhost when running into this?

[ableegoldman]

Regardless of the above, we do ultimately want to set this to kafka-music-application as you've done. I believe this patch should be applied to 5.1.3 branch and later -- could you retarget the PR against 5.1.3-post so we can merge it downstream from there? You may need to rebase, or feel free to just open a new PR and ping us.

Thanks!

[pantrif]

Hello @ableegoldman!! Indeed I submit this fix a few minutes after you merged. The localhost part was the problematic one. So I was hitting this issue before you make the above change.
However, I tried a few things of my own like setting the host to 127.0.0.1 or to 0.0.0.0 like you did and both seems to work just fine.
But I believe since you have already set up a host in the docker-compose file (hostname: kafka-music-application) I found better to provide that host (because 0.0.0.0 is too generic)