fix: add trace for StreamStatus (#2081)

This adds a trace for the code that runs when a client requests the
StreamStatus.

Ref: SRX-8PS60H

services/rollout-service/pkg/service/broadcast.go

@@ -19,6 +19,7 @@ package service
 import (
 	"context"
 	"errors"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
 	"sync"
 	"time"
 
@@ -176,15 +177,21 @@ func (b *Broadcast) DisconnectAll() {
 	b.listener = make(map[chan *BroadcastEvent]struct{})
 }
 
-func (b *Broadcast) StreamStatus(req *api.StreamStatusRequest, svc api.RolloutService_StreamStatusServer) error {
+func (b *Broadcast) StreamStatus(_ *api.StreamStatusRequest, svc api.RolloutService_StreamStatusServer) error {
+	ctx := svc.Context()
+	span, ctx := tracer.StartSpanFromContext(ctx, "StreamStatusConnect")
+	defer span.Finish()
 	resp, ch, unsubscribe := b.Start()
 	defer unsubscribe()
+	span.SetTag("numberOfEvents", len(resp))
 	for _, r := range resp {
 		err := svc.Send(streamStatus(r))
 		if err != nil {
 			return err
 		}
 	}
+	span.Finish()
+
 	for {
 		select {
 		case r := <-ch:
@@ -196,8 +203,8 @@ func (b *Broadcast) StreamStatus(req *api.StreamStatusRequest, svc api.RolloutSe
 			if err != nil {
 				return err
 			}
-		case <-svc.Context().Done():
-			err := svc.Context().Err()
+		case <-ctx.Done():
+			err := ctx.Err()
 			if errors.Is(err, context.Canceled) {
 				return nil
 			}