Task: Get all mailboxes from Help Scout

n8n workflow JSON:
{"nodes":[{"name":"On clicking 'execute'","type":"n8n-nodes-base.manualTrigger","position":[250,300],"parameters":{},"typeVersion":1},{"name":"HelpScout","type":"n8n-nodes-base.helpScout","position":[450,300],"parameters":{"resource":"mailbox","operation":"getAll"},"credentials":{"helpScoutOAuth2Api":"helpscout_creds"},"typeVersion":1}],"connections":{"On clicking 'execute'":{"main":[[{"node":"HelpScout","type":"main","index":0}]]}}}