Review and enhance tracing support for ad service service (Java)

[cartersocha]

The following is a list of requirements that we need to evaluate before declaring v1 for trace telemetry. These requirements are across the entire application; Not all services will meet all requirements. Determine the relevant features for this service.

• Automatic Instrumentation is being used where appropriate.
• Library instrumentation is being used if automatic instrumentation is unavailable.
• Services extend automatic instrumentation. #151
  • New attributes/events attached to existing spans. #152
  • New spans are being created from existing spans.
• Automatic and Manual Context Propagation are being demonstrated.
  • Interprocess context propagation is demonstrated.
• Telemetry is not being sampled upfront.
• Telemetry is not being filtered upfront.
• Baggage is being set and read appropriately (i.e., baggage must be explicitly set as attributes on spans)

Referencing: #42

Service: https://github.com/open-telemetry/opentelemetry-demo-webstore/blob/main/src/adservice/README.md

[puckpuck]

Should we check this one as well for Java?

• Library instrumentation is being used if automatic instrumentation is unavailable.

[julianocosta89]

@puckpuck we could maybe add a Feature Flag to decide if the Jave OTel Agent will or not be deployed to the AdService.
And when not, then the library instrumentation should be there.