Fix n.Expiration.IsZero and support pushtotalk push notification (#235)

Author: deltapath-eric

client_test.go

@@ -352,6 +352,17 @@ func TestPushTypeLiveActivityHeader(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+func TestPushTypePushToTalkHeader(t *testing.T) {
+	n := mockNotification()
+	n.PushType = apns.PushTypePushToTalk
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "pushtotalk", r.Header.Get("apns-push-type"))
+	}))
+	defer server.Close()
+	_, err := mockClient(server.URL).Push(n)
+	assert.NoError(t, err)
+}
+
 func TestAuthorizationHeader(t *testing.T) {
 	n := mockNotification()
 	token := mockToken()

notification.go

@@ -71,6 +71,12 @@ const (
 	// push type is recommended for iOS. It is not available on macOS, tvOS,
 	// watchOS and iPadOS.
 	PushTypeLiveActivity EPushType = "liveactivity"
+
+	// PushTypePushToTalk is used for notifications that provide information about the
+	// push to talk. If you set this push type, the apns-topic header field
+	// must use your app’s bundle ID with.voip-ptt appended to the end.
+	// The pushtotalk push type isn’t available on watchOS, macOS, and tvOS. It’s recommended on iOS and iPadOS.
+	PushTypePushToTalk EPushType = "pushtotalk"
 )
 
 const (