Send message action

[Lacah]

This action enables asynchronous communication between flows by using the sn_fd.FlowAPI.sendMessage() method to deliver a message to a specified flow context. It is useful for building event-driven or distributed process logic where different flows need to signal each other’s progress or completion.

Inputs:

• context_id (String, required) - The context ID of the target flow waiting for a message.
• message (String, required) - The message payload to send.
• payload (String, optional) - A payload that is accessible by subsequent actions in the targeted flow.

Behavior:
When executed, the action should call the Flow API to send the provided message to the specified context ID:
sn_fd.FlowAPI.sendMessage(inputs.context_id, inputs.message, inputs.payload);

Since this API method does not return anything, the action's output is simply about whether or not the script was executed successfully.

Resolves #146

[github-actions]

✅ Valid PR for ActionPack

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