The message content payload
The registered message type identifier (e.g. 'RC:TxtMsg')
List of target user IDs for directed messages. Only these users will receive the message.
If true, suppress push notifications for this message
If true, this message will not update the channel's last message
If true, request read receipt for this message
Key-value metadata (expansion) to attach to the message
Push notification configuration for this message
Callback invoked before the message is sent, providing the local message instance
Text message content
Parameters for sending a text message.