merge: #9468

9468: [Backport stable/8.0] Set zbctl user agent r=Zelldon a=backport-action

# Description
Backport of #9434 to `stable/8.0`.

relates to 

Co-authored-by: Christopher Zell <zelldon91@googlemail.com>

clients/go/cmd/zbctl/internal/commands/root.go

@@ -131,6 +131,7 @@ var initClient = func(cmd *cobra.Command, args []string) error {
 	client, err = zbc.NewClient(&zbc.ClientConfig{
 		GatewayAddress:      fmt.Sprintf("%s:%s", host, port),
 		CredentialsProvider: credsProvider,
+		UserAgent:           "zeebe-client-zbctl/" + Version,
 	})
 	return err
 }

clients/go/pkg/zbc/client.go

@@ -65,7 +65,10 @@ type ClientConfig struct {
 	// of 45 seconds being used
 	KeepAlive time.Duration
 
-	DialOpts []grpc.DialOption
+	// UserAgent is an optional field, to specify the user-agent header which should be sent by each
+	// gRPC request. Defaults to zeebe-client-go/%version.
+	UserAgent string
+	DialOpts  []grpc.DialOption
 }
 
 // ErrFileNotFound is returned whenever a file can't be found at the provided path. Use this value to do error comparison.
@@ -158,7 +161,11 @@ func NewClient(config *ClientConfig) (Client, error) {
 		return nil, err
 	}
 
-	config.DialOpts = append(config.DialOpts, grpc.WithUserAgent("zeebe-client-go/"+getVersion()))
+	if config.UserAgent == "" {
+		config.UserAgent = "zeebe-client-go/" + getVersion()
+	}
+
+	config.DialOpts = append(config.DialOpts, grpc.WithUserAgent(config.UserAgent))
 
 	conn, err := grpc.Dial(config.GatewayAddress, config.DialOpts...)
 	if err != nil {

clients/go/pkg/zbc/client_test.go

@@ -18,6 +18,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"github.com/camunda/zeebe/clients/go/v8/internal/utils"
+	"google.golang.org/grpc/metadata"
 	"net"
 	"strconv"
 	"strings"
@@ -164,6 +166,61 @@ func (s *clientTestSuite) TestGatewayAddressEnvVar() {
 	s.EqualValues(fmt.Sprintf("0.0.0.0:%s", parts[len(parts)-1]), config.GatewayAddress)
 }
 
+func (s *clientTestSuite) TestDefaultUserAgent() {
+	// given
+	var incomingContext = make(map[string][]string)
+	lis, server := createServerWithUnaryInterceptor(func(ctx context.Context, _ interface{}, _ *grpc.UnaryServerInfo, _ grpc.UnaryHandler) (interface{}, error) {
+		incomingContext, _ = metadata.FromIncomingContext(ctx)
+		return nil, nil
+	})
+	go server.Serve(lis)
+	defer server.Stop()
+
+	// when
+	client, err := NewClient(&ClientConfig{
+		GatewayAddress:         lis.Addr().String(),
+		UsePlaintextConnection: true,
+	})
+	s.Require().NoError(err)
+	ctx, cancel := context.WithTimeout(context.Background(), utils.DefaultTestTimeout)
+	defer cancel()
+
+	_, _ = client.NewTopologyCommand().Send(ctx)
+	userAgent := incomingContext["user-agent"]
+
+	// then
+	s.Require().Len(userAgent, 1)
+	s.Require().Contains(userAgent[0], "zeebe-client-go/"+getVersion())
+}
+
+func (s *clientTestSuite) TestSpecificUserAgent() {
+	// given
+	var incomingContext = make(map[string][]string)
+	lis, server := createServerWithUnaryInterceptor(func(ctx context.Context, _ interface{}, _ *grpc.UnaryServerInfo, _ grpc.UnaryHandler) (interface{}, error) {
+		incomingContext, _ = metadata.FromIncomingContext(ctx)
+		return nil, nil
+	})
+	go server.Serve(lis)
+	defer server.Stop()
+
+	// when
+	client, err := NewClient(&ClientConfig{
+		GatewayAddress:         lis.Addr().String(),
+		UsePlaintextConnection: true,
+		UserAgent:              "anotherUserAgentLikeZbctl",
+	})
+	s.Require().NoError(err)
+	ctx, cancel := context.WithTimeout(context.Background(), utils.DefaultTestTimeout)
+	defer cancel()
+
+	_, _ = client.NewTopologyCommand().Send(ctx)
+	userAgent := incomingContext["user-agent"]
+
+	// then
+	s.Require().Len(userAgent, 1)
+	s.Require().Contains(userAgent[0], "anotherUserAgentLikeZbctl")
+}
+
 func (s *clientTestSuite) TestCaCertificateEnvVar() {
 	// given
 	lis, grpcServer := createSecureServer(false)