api/resolver: update resolver to enable subdomain routing (#1747)

* api/resolver: update domain / service prefix usage

* api/resolver/subdomain: implement subdomain resolver for domain resolution

* api/handler: fix tests

api/resolver/resolver.go

@@ -27,18 +27,6 @@ type Endpoint struct {
 	Method string
 	// HTTP Path e.g /greeter.
 	Path string
-}
-
-type Options struct {
-	Handler   string
-	Namespace func(*http.Request) string
-}
-
-type Option func(o *Options)
-
-// StaticNamespace returns the same namespace for each request
-func StaticNamespace(ns string) func(*http.Request) string {
-	return func(*http.Request) string {
-		return ns
-	}
+	// Domain endpoint exists within
+	Domain string
 }