Optional property that overrides the default way the content will be shared to messenger
@property (nonatomic, readwrite, strong) FBSDKMessengerContext *contextOverride;
By default, if a user enters your app via a replyable context in Messenger (for instance, tapping Reply on a message or opening your app from composer), the next share out of your app will trigger the reply flow in Messenger by default. If you'd prefer to not trigger the reply flow, then overriding this with FBSDKMessengerBroadcastContext will trigger the broadcast flow in messenger.
Pass additional information to be sent to Messenger which is sent back to the user's app when they reply to an attributed message.
@property (nonatomic, readwrite, copy) NSString *metadata;
Optional property describing the www source URL of the content
@property (nonatomic, readwrite, copy) NSURL *sourceURL;
Setting this property improves performance by allowing Messenger to download the content directly rather than uploading the content from your app. This option is only used for animated GIFs and WebPs