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/subdomain/subdomain_test.go

@@ -0,0 +1,71 @@
+package subdomain
+
+import (
+	"net/http"
+	"net/url"
+	"testing"
+
+	"github.com/micro/go-micro/v2/api/resolver/vpath"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestResolve(t *testing.T) {
+	tt := []struct {
+		Name   string
+		Host   string
+		Result string
+	}{
+		{
+			Name:   "Top level domain",
+			Host:   "micro.mu",
+			Result: "micro",
+		},
+		{
+			Name:   "Effective top level domain",
+			Host:   "micro.com.au",
+			Result: "micro",
+		},
+		{
+			Name:   "Subdomain dev",
+			Host:   "dev.micro.mu",
+			Result: "dev",
+		},
+		{
+			Name:   "Subdomain foo",
+			Host:   "foo.micro.mu",
+			Result: "foo",
+		},
+		{
+			Name:   "Multi-level subdomain",
+			Host:   "staging.myapp.m3o.app",
+			Result: "myapp-staging",
+		},
+		{
+			Name:   "Dev host",
+			Host:   "127.0.0.1",
+			Result: "micro",
+		},
+		{
+			Name:   "Localhost",
+			Host:   "localhost",
+			Result: "micro",
+		},
+		{
+			Name:   "IP host",
+			Host:   "81.151.101.146",
+			Result: "micro",
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.Name, func(t *testing.T) {
+			r := NewResolver(vpath.NewResolver())
+			result, err := r.Resolve(&http.Request{URL: &url.URL{Host: tc.Host, Path: "foo/bar"}})
+			assert.Nil(t, err, "Expecter err to be nil")
+			if result != nil {
+				assert.Equal(t, tc.Result, result.Domain, "Expected %v but got %v", tc.Result, result.Domain)
+			}
+		})
+	}
+}