There are currently two solutions for this:
- Use this community node: n8n-nodes-run-node-with-credentials-x - npm - credentials can be created using the n8n API
- Use custom auth in an HTTP request, like in this example: Turn Emails into AI-Enhanced Tasks in Notion (Multi-User Support) with Gmail, Airtable and Softr | n8n workflow template
This should also be doable with OAuth by adding a few extra steps.