Ability to print labels from extension capabilities (fixes #339)

proxy.go

@@ -98,6 +98,11 @@ func (c caps) capabilities(fn func(m map[string]interface{}, w3c bool)) {
 				if alwaysMatch, ok := m[keys.alwaysMatch]; ok {
 					if m, ok := alwaysMatch.(map[string]interface{}); ok {
 						fn(m, true)
+						for k, v := range m { // Extension capabilities have ":" in key
+							if ec, ok := v.(map[string]interface{}); ok && strings.Contains(k, ":") {
+								fn(ec, true)
+							}
+						}
 					}
 				}
 			}

proxy_test.go

@@ -880,7 +880,7 @@ func TestStartSessionWithDefaultVersionW3C(t *testing.T) {
 	mux.HandleFunc("/wd/hub/session", postOnly(func(w http.ResponseWriter, r *http.Request) {
 		body, _ := ioutil.ReadAll(r.Body)
 		r.Body.Close()
-		var sess map[string]map[string]map[string]string
+		var sess map[string]map[string]map[string]interface{}
 		err := json.Unmarshal(body, &sess)
 		w.Write([]byte(`{"sessionId":"123"}`))
 		AssertThat(t, err, Is{nil})
@@ -911,7 +911,7 @@ func TestStartSessionWithDefaultVersionW3C(t *testing.T) {
 		}}}}
 	updateQuota(user, browsers)
 
-	createSession(`{"capabilities":{"alwaysMatch":{"browserName":"browser"}}}`)
+	createSession(`{"capabilities":{"alwaysMatch":{"browserName":"browser", "selenoid:options": {"labels": {"some-key": "some-value"}}}}}`)
 }
 
 func TestClientClosedConnection(t *testing.T) {