collab: Attach user_id to LLM spans (#16311)

This PR updates the LLM service to attach the user ID to the spans.

Release Notes:

- N/A

crates/collab/src/llm.rs

@@ -138,7 +138,9 @@ async fn validate_api_token<B>(mut req: Request<B>, next: Next<B>) -> impl IntoR
                 ));
             }
 
-            tracing::Span::current().record("authn.jti", &claims.jti);
+            tracing::Span::current()
+                .record("user_id", claims.user_id)
+                .record("authn.jti", &claims.jti);
 
             req.extensions_mut().insert(claims);
             Ok::<_, Error>(next.run(req).await.into_response())