Include `gen_ai.conversation.id` in OTEL spans

[pedelman]

Is your feature request related to a problem? Please describe.
I am exploring AI Evals platforms with adk-go and notice that each message in the conversation is not linked together when using the OTEL integration. When I checked the spans, it seems like the gen_ai.conversation.id is not included currently.

It does look like adk-go supplies:

gcp.vertex.agent.session_id: UUID

I dont think we would need to remove this span attribute, we can just add the gen_ai semantic convention as an additive change.

Describe the solution you'd like
I would like the conversation session id to be passes as the gen_ai.conversation.id so messages can be linked together across multiple traces within the Evals platform.

Looks like it can be set here:

adk-go/internal/telemetry/telemetry.go

Line 209 in d13c2dd

attribute.String(gcpVertexAgentSessionID, agentCtx.Session().ID()),

Describe alternatives you've considered
If there are any workarounds, I would certainly be open to this. Otherwise I can work on a custom fork for the time being.

Additional context

• OTEL GenAI Semantic Conventions - https://opentelemetry.io/docs/specs/semconv/gen-ai/gen-ai-spans/

[jrmolin]

could this be expanded to include an example where one can define an endpoint and then see all of the OTel data, for example Arize-AI's Phoenix endpoint? it's trivial to do this in python, but i don't see how to get it done in Golang.