feat(source/http): Add User Agent to calls (#1102)

This change adds a User Agent for all http calls as part of source. This
will append the user agent being passed as part of prebuilt tools
context to default headers.

internal/sources/http/http.go

@@ -93,6 +93,18 @@ func (r Config) Initialize(ctx context.Context, tracer trace.Tracer) (sources.So
 		return nil, fmt.Errorf("failed to parse BaseUrl %v", err)
 	}
 
+	ua, err := util.UserAgentFromContext(ctx)
+	if err != nil {
+		fmt.Printf("Error in User Agent retrieval: %s", err)
+	}
+	if r.DefaultHeaders == nil {
+		r.DefaultHeaders = make(map[string]string)
+	}
+	if existingUA, ok := r.DefaultHeaders["User-Agent"]; ok {
+		ua = ua + " " + existingUA
+	}
+	r.DefaultHeaders["User-Agent"] = ua
+
 	s := &Source{
 		Name:           r.Name,
 		Kind:           SourceKind,

internal/tools/http/http.go

@@ -31,7 +31,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	httpsrc "github.com/googleapis/genai-toolbox/internal/sources/http"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 )
 
 const kind string = "http"
@@ -314,10 +313,6 @@ func (t Tool) Invoke(ctx context.Context, params tools.ParamValues) (any, error)
 		req.Header.Set(k, v)
 	}
 
-	if ua, err := util.UserAgentFromContext(ctx); err == nil {
-		req.Header.Set("User-Agent", ua)
-	}
-
 	// Make request and fetch response
 	resp, err := t.Client.Do(req)
 	if err != nil {

internal/tools/utility/alloydbwaitforoperation/alloydbwaitforoperation.go

@@ -30,7 +30,6 @@ import (
 	"github.com/googleapis/genai-toolbox/internal/sources"
 	httpsrc "github.com/googleapis/genai-toolbox/internal/sources/http"
 	"github.com/googleapis/genai-toolbox/internal/tools"
-	"github.com/googleapis/genai-toolbox/internal/util"
 )
 
 const kind string = "alloydb-wait-for-operation"
@@ -256,10 +255,6 @@ func (t *Tool) Invoke(ctx context.Context, params tools.ParamValues) (any, error
 			req.Header.Set(k, v)
 		}
 
-		if ua, err := util.UserAgentFromContext(ctx); err == nil {
-			req.Header.Set("User-Agent", ua)
-		}
-
 		resp, err := t.Client.Do(req)
 		if err != nil {
 			fmt.Printf("error making HTTP request during polling: %s, retrying in %v\n", err, delay)