Task: Send Onfleet driver signup messages in Slack

n8n workflow JSON:
{"id":14,"name":"Onfleet Driver signup message in Slack","nodes":[{"name":"Onfleet Trigger","type":"n8n-nodes-base.onfleetTrigger","position":[460,300],"webhookId":"a005e163-13a2-4ea2-a127-6e00e30a82f4","parameters":{"triggerOn":"workerCreated","additionalFields":{}},"credentials":{"onfleetApi":{"id":"2","name":"Onfleet API Key"}},"typeVersion":1},{"name":"Slack","type":"n8n-nodes-base.slack","position":[680,300],"parameters":{"text":"A new driver has signed up!","channel":"#new-driver-signup","attachments":[],"otherOptions":{}},"credentials":{"slackApi":{"id":"7","name":"Slack account"}},"typeVersion":1}],"active":false,"settings":{},"connections":{"Onfleet Trigger":{"main":[[{"node":"Slack","type":"main","index":0}]]}}}