Make OTEL exporter headers configurable e.g. pass Authorization header.

[robwdux]

Is your feature request related to a problem? Please describe.

The Honeycomb OTEL SDK wrapper does not expose configuring the exporter headers. We need to authorize sending telemetry via our backend (OpenTelemetry Collector) as we do our application APIs.

Describe the solution you'd like

Either arbitrary header configuration or e.g. endpointAuthHeaderValue

Describe alternatives you've considered

Additional context

• https://github.com/honeycombio/honeycomb-opentelemetry-web/tree/main?tab=readme-ov-file#send-to-an-opentelemetry-collector

• honeycomb-opentelemetry-web/src/http-json-trace-exporter.ts

  Lines 19 to 22 in 877f2f1

  	headers: {
  	[TEAM_HEADER_KEY]: apiKey,
  	[DATASET_HEADER_KEY]: isClassic(apiKey) ? options?.dataset : undefined,
  	},