fix: dropped support for x-instana-service header

[aryamohanan]

The capture of the X-Instana-Service header value as span.data.service has been removed from the tracer. According to the public documentation here:

By setting the X-Instana-Service HTTP header on a call, the destination service (the one receiving the HTTP request) is tagged with the value provided in the header.

Note: The X-Instana-Service HTTP header is not collected automatically. To use it, the Instana agent must be configured, as explained in "Capturing custom HTTP headers".

By default, Instana does not capture HTTP headers during tracing. However, you can configure HTTP header capture by modifying the agent's configuration file (/etc/instana/configuration.yaml) as follows:

com.instana.tracing:
  extra-http-headers:
    - 'X-Instana-Service'

The backend extracting the service name from the captured header.
Therefore, implementing this directly within our tracer by inspecting the X-Instana-Service header and adding the annotation is redundant. For this reason, the Instana tracer community has chosen not to capture the X-Instana-Service header within the tracer.

[kirrg001]

Thanks!

Note: The X-Instana-Service HTTP header is not automatically collected. For it to work, the Instana agent must be configured , see "Capturing custom HTTP headers".

FYI Docs links are broken.

This is the correct link:
https://www.ibm.com/docs/en/instana-observability/current?topic=cha-configuring-host-agents-by-using-agent-configuration-file#capturing-custom-http-headers

We will fix it soon!

[kirrg001]

Suggestion for commit body:

• BREAKING CHANGE: ...
• Migration: Please define the header in the agent config...blabla