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>

tracer/noop.go

@@ -2,24 +2,24 @@ package tracer
 
 import "context"
 
-type noop struct{}
+type NoopTracer struct{}
 
-func (n *noop) Init(...Option) error {
+func (n *NoopTracer) Init(...Option) error {
 	return nil
 }
 
-func (n *noop) Start(ctx context.Context, name string) (context.Context, *Span) {
+func (n *NoopTracer) Start(ctx context.Context, name string) (context.Context, *Span) {
 	return nil, nil
 }
 
-func (n *noop) Finish(*Span) error {
+func (n *NoopTracer) Finish(*Span) error {
 	return nil
 }
 
-func (n *noop) Read(...ReadOption) ([]*Span, error) {
+func (n *NoopTracer) Read(...ReadOption) ([]*Span, error) {
 	return nil, nil
 }
 
-func newTracer(opts ...Option) Tracer {
-	return &noop{}
+func NewTracer(opts ...Option) Tracer {
+	return &NoopTracer{}
 }