The parameters for creating a thread if the supplied thread doesn't exist yet. If the thread doesn't exist but createThread isn't provided, the call will generate an error. This value is ignored if the thread already exists.
This is an object with the following fields:
The name of the thread. This is shown to users when the thread is referenced, such as in notifications. This should generally be something like the page title.
A URL where the thread can be seen. This determines where a user is sent when they click on a reference to this thread, such as in a notification, or if they click on a reference to a message in the thread and the message doesn't have its own URL.
The URL of the icon to show next to the message. This is only used for action_message messages; other messages show the avatar of the author. If an action_message does not have an icon set, no icon is shown.
The type of message this is. A user_message is a message that the author sent. An action_message is a message about something that happened, such as the thread being resolved. The default value is user_message.