Send the given message to the specified channel on execution. No input table needs to be specified, if one is given it is passed through verbatim.

API call details: https://api.slack.com/methods/chat.postMessage

Notes on username: By default the message will be sent and display with the apps name. If the chat:write:customize scope has been added then it is possible to set a username parameter. If changing the display name / username of the source of the message is desirable then check 'Set username' and provide the username to post the message as.

Rate Limiting: The underlying Java Slack API offers an async approach where it attempts to manage Rate Limits on API requests. This node node uses the aysnc version of the method and will send approximately 1 message per second.