Add OSInAppMessage

* Add OSInAppMessage to OSFlutterCategories

Author: tanaynigam

ios/Classes/OSFlutterCategories.h

@@ -43,6 +43,10 @@
 - (NSDictionary *)toJson;
 @end
 
+@interface OSInAppMessage (Flutter)
+- (NSDictionary *)toJson;
+@end
+
 @interface NSError (Flutter)
 - (FlutterError *)flutterError;
 @end

ios/Classes/OSFlutterCategories.m

@@ -97,6 +97,16 @@ - (NSDictionary *)toJson {
 }
 @end
 
+@implementation OSInAppMessage (Flutter)
+- (NSDictionary *)toJson {
+    NSMutableDictionary *json = [NSMutableDictionary new];
+
+    json[@"message_id"] = self.messageId;
+
+    return json;
+}
+@end
+
 @implementation NSError (Flutter)
 - (FlutterError *)flutterError {
     return [FlutterError errorWithCode:[NSString stringWithFormat:@"%i", (int)self.code] message:self.localizedDescription details:nil];