Proxy HTTP request headers from VS Code

[rohitsanj]

Summary of Changes

Include all headers passed from VS Code when proxying requests to a target Kafka/SR cluster, except for sidecar-specific headers (specified as config in application.yml).

Resolves #92

Any additional details or context that should be provided?

Pull request checklist

Please check if your PR fulfills the following (if applicable):

• Tests:
  • Added new
  • Updated existing
  • Deleted existing
• Have you validated this change locally against a running instance of the Quarkus dev server?

  make quarkus-dev

• Have you validated this change against a locally running native executable?

  make mvn-package-native && ./target/ide-sidecar-*-runner

[rhauch]

LGTM

[jlrobins]

Worked with Rohit and fixed some issues found in clicktesting. We wrote #102 in the process thereof.

But this works better than before now. Can now POST to create a schema consistently now that content-type header is making it through to ccloud.