feat: allow to pass extra data to upstreams endpoints

[alekseyvdovenko]

Occasionally for providing a sophisticated load balancing it's essential to pass an extra metadata to the upstreams, so the destination/adapter will have a better context of how to process the request. The idea is to extend the current configuration for the upstreams by introducing a new optional block extraData which will be passed to a particular upstream endpoint as header X-UPSTREAM-EXTRA-DATA.

Example of the configuration:

{
  "models": {
    "llm": {
      "type": "chat",
      "upstreams": [
        {
          "extraData": {
            "<key-1>":"<value-1>",
            "<key-2>":"<value-2>"
          }
        },
        {
          "extraData": {
            "<key-3>":"<value-3>",
            "<key-4>":"<value-4>"
          }
        }
      ]
    }
  }
}

[alekseyvdovenko]

/deploy-review

Environment URL: https://chat-ai-dial-core-pr-470.nightly-test.deltixhub.io E2E tests status: success

[alekseyvdovenko]

This is the blocker for https://github.com/epam/ai-dial-adapter-bedrock/issues/126

[sdryapko]

@astsiapanay please review

[alekseyvdovenko]

/deploy-review

Environment URL: https://chat-ai-dial-core-pr-470.nightly-test.deltixhub.io E2E tests status: failed

[alekseyvdovenko]

/deploy-review

Environment URL: https://chat-ai-dial-core-pr-470.nightly-test.deltixhub.io E2E tests status: success