Telemetry instrumentation config for http_client headers

[bonnici]

Adds a new telemetry instrumentation configuration for the http_client spans. This setting allows request headers added by Rhai scripts to be attached to the http_client span.

For example, with a Rhai script:

fn subgraph_service(service, subgraph) {
  let request_callback = |request| {
      print(`Subgraph service: Ready to send sub-operation to subgraph ${subgraph}`);
      request.subgraph.headers["some_rhai_request_header"] = "request-header-from-rhai";
  };
  
  let response_callback = |response| {
      print(`Subgraph service: Received sub-operation response from subgraph ${subgraph}`);
      response.headers["some_rhai_response_header"] = "response-header-from-rhai";
  };

  service.map_request(request_callback);
  service.map_response(response_callback);
}

The following configuration adds the some_rhai_request_header value to the http_client span. The some_rhai_response_header value is available on the subgraph span as before.

telemetry:
  instrumentation:
    spans:
      mode: spec_compliant
      subgraph:
        attributes:
          http.response.header.some_rhai_response_header:
            subgraph_response_header: "some_rhai_response_header"
      http_client:
        attributes:
          http.request.header.some_rhai_request_header:
            http_client_request_header: "some_rhai_request_header"

---

Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• PR description explains the motivation for the change and relevant context for reviewing
• PR description links appropriate GitHub/Jira tickets (creating when necessary)
• Changeset is included for user-facing changes
• Changes are compatible¹
• Documentation² completed
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• Metrics and logs are added³ and documented
• Tests added and passing⁴
  • Unit tests
  • [] Integration tests
  • Manual tests, as necessary

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Notes

Footnotes

1. It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this. ↩

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[apollo-librarian]

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File Changes

0 new, 2 changed, 0 removed

* graphos/routing/(latest)/observability/router-telemetry-otel/enabling-telemetry/selectors.mdx
* graphos/routing/(latest)/observability/router-telemetry-otel/enabling-telemetry/spans.mdx

Build ID: c4f3c82b102b7882bca48036
Build Logs: View logs

URL: https://www.apollographql.com/docs/deploy-preview/c4f3c82b102b7882bca48036

[BrynCooke]

Looks great, only a couple of renames and selectors.mdx needs updating.

[BrynCooke]

We need to add a new section to https://github.com/apollographql/router/blob/njmnjm/ROUTER-1068/subgraph-rhai-header-telemetry/docs/source/routing/observability/router-telemetry-otel/enabling-telemetry/selectors.mdx that has the two new selectors that you've added