many improvements with options and noop stuff

* add many options helpers
* fix noop client to allow publish messages to topic in broker
* fix noop server to allow registering in registry
* fix noop server to allow subscribe to topic in broker
* fix new service initialization

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

server/registry.go

@@ -0,0 +1,89 @@
+package server
+
+import (
+	"net"
+	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
+	"github.com/unistack-org/micro/v3/registry"
+	"github.com/unistack-org/micro/v3/util/addr"
+	"github.com/unistack-org/micro/v3/util/backoff"
+)
+
+var (
+	// DefaultRegisterFunc uses backoff to register service
+	DefaultRegisterFunc = func(service *registry.Service, config Options) error {
+		var err error
+
+		opts := []registry.RegisterOption{
+			registry.RegisterTTL(config.RegisterTTL),
+			registry.RegisterDomain(config.Namespace),
+		}
+
+		for i := 0; i <= config.RegisterAttempts; i++ {
+			err = config.Registry.Register(service, opts...)
+			if err == nil {
+				break
+			}
+			// backoff then retry
+			time.Sleep(backoff.Do(i + 1))
+			continue
+		}
+		return err
+	}
+	// DefaultDeregisterFunc uses backoff to deregister service
+	DefaultDeregisterFunc = func(service *registry.Service, config Options) error {
+		var err error
+
+		opts := []registry.DeregisterOption{
+			registry.DeregisterDomain(config.Namespace),
+		}
+
+		for i := 0; i <= config.DeregisterAttempts; i++ {
+			err = config.Registry.Deregister(service, opts...)
+			if err == nil {
+				break
+			}
+			// backoff then retry
+			time.Sleep(backoff.Do(i + 1))
+			continue
+		}
+		return err
+	}
+)
+
+func NewRegistryService(s Server) (*registry.Service, error) {
+	opts := s.Options()
+
+	advt := opts.Address
+	if len(opts.Advertise) > 0 {
+		advt = opts.Advertise
+	}
+
+	host, port, err := net.SplitHostPort(advt)
+	if err != nil {
+		return nil, err
+	}
+
+	addr, err := addr.Extract(host)
+	if err != nil {
+		addr = host
+	}
+
+	node := &registry.Node{
+		Id:      opts.Name + "-" + opts.Id,
+		Address: net.JoinHostPort(addr, port),
+	}
+	node.Metadata = metadata.Copy(opts.Metadata)
+
+	node.Metadata["server"] = s.String()
+	node.Metadata["broker"] = opts.Broker.String()
+	node.Metadata["registry"] = opts.Registry.String()
+
+	return &registry.Service{
+		Name:     opts.Name,
+		Version:  opts.Version,
+		Nodes:    []*registry.Node{node},
+		Metadata: metadata.New(0),
+	}, nil
+}