add wip deregistering

lib/models/requests/deregister_pusher.dart

@@ -0,0 +1,13 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+
+part "deregister_pusher.freezed.dart";
+part "deregister_pusher.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const DeregisterPusherRequest({
+  required final String appId,
+  @JsonKey(name: "pushkey") required final String pushKey,
+}) with _$DeregisterPusherRequest {
+  Map<String, Object?> toJson() => _$DeregisterPusherRequestToJson(this);
+}