Task: Send a message on Mattermost when a workflow is updated

n8n workflow JSON:
{"nodes":[{"name":"Webhook","type":"n8n-nodes-base.webhook","position":[490,460],"webhookId":"c0345765-4488-4ac8-a9da-02f647dd2b90","parameters":{"path":"c0345765-4488-4ac8-a9da-02f647dd2b90","options":{}},"typeVersion":1},{"name":"Set","type":"n8n-nodes-base.set","position":[690,460],"parameters":{"values":{"string":[{"name":"Message","value":"Hello!"}]},"options":{},"keepOnlySet":true},"typeVersion":1},{"name":"Mattermost","type":"n8n-nodes-base.mattermost","position":[690,610],"parameters":{"message":"=The workflow {{$workflow.name}}, was updated.","channelId":"toyi3uoycf8rirtm7d5jm15sso","attachments":[],"otherOptions":{}},"credentials":{"mattermostApi":"Mattermost Credentials"},"typeVersion":1},{"name":"Workflow Trigger","type":"n8n-nodes-base.workflowTrigger","position":[490,610],"parameters":{"events":["update"]},"typeVersion":1}],"connections":{"Webhook":{"main":[[{"node":"Set","type":"main","index":0}]]},"Workflow Trigger":{"main":[[{"node":"Mattermost","type":"main","index":0}]]}}}