feat(fcm): Add LiveActivityToken to ApnsConfig for iOS live activities support (#454)

* feat(fcm): Add LiveActivityToken to ApnsConfig for iOS live activities support

* Empty commit message

Author: kanclalg

FirebaseAdmin/FirebaseAdmin.Tests/Messaging/MessageTest.cs

@@ -1013,6 +1013,7 @@ public void ApnsConfig()
                         AnalyticsLabel = "label",
                         ImageUrl = "https://example.com/image.png",
                     },
+                    LiveActivityToken = "token",
                 },
             };
             var expected = new JObject()
@@ -1056,6 +1057,9 @@ public void ApnsConfig()
                                 { "image", "https://example.com/image.png" },
                             }
                         },
+                        {
+                            "live_activity_token", "token"
+                        },
                     }
                 },
             };

FirebaseAdmin/FirebaseAdmin/Messaging/ApnsConfig.cs

@@ -75,6 +75,14 @@ public IDictionary<string, object> CustomData
             }
         }
 
+        /// <summary>
+        /// Gets or sets the APNs token used for live activities on iOS. Refer
+        /// to <a href="https://firebase.google.com/docs/cloud-messaging/ios/live-activity">
+        /// Firebase live activity documentation</a> for more information.
+        /// </summary>
+        [JsonProperty("live_activity_token")]
+        public string LiveActivityToken { get; set; }
+
         /// <summary>
         /// Gets or sets the APNs payload as accepted by the FCM backend servers.
         /// </summary>
@@ -108,6 +116,7 @@ internal ApnsConfig CopyAndValidate()
                 Headers = this.Headers?.Copy(),
                 Payload = this.Payload.CopyAndValidate(),
                 FcmOptions = this.FcmOptions?.CopyAndValidate(),
+                LiveActivityToken = this.LiveActivityToken,
             };
             return copy;
         }