Deprecate client/selector (#1767)

* client/{grpc,rpc}: depricate selector (wip)

* {client,cmd}: remove client/selector

* deprecate client/selector

* router/static: fix lookup

* config/cmd: add support for legacy static selector flag

* config/cmd: add support for legacy dns selector flag

api/handler/util/router.go

@@ -0,0 +1,32 @@
+package util
+
+import (
+	"github.com/micro/go-micro/v2/registry"
+	"github.com/micro/go-micro/v2/router"
+)
+
+// Router is a hack for API routing
+func Router(srvs []*registry.Service) router.Router {
+	var routes []router.Route
+
+	for _, srv := range srvs {
+		for _, n := range srv.Nodes {
+			routes = append(routes, router.Route{Address: n.Address, Metadata: n.Metadata})
+		}
+	}
+
+	return &apiRouter{routes: routes}
+}
+
+func (r *apiRouter) Lookup(...router.QueryOption) ([]router.Route, error) {
+	return r.routes, nil
+}
+
+type apiRouter struct {
+	routes []router.Route
+	router.Router
+}
+
+func (r *apiRouter) String() string {
+	return "api"
+}