It would be nice to be able to use Google Service Account Authentication for generic REST APIs. It could work the same way as for BigQuery, Storage and Firestore.
This would be useful for calling APIs deployed with Google Endpoints. With Endpoints I can deploy generic API backends and put service account authentication on top easily. If I could call these APIs with service account auth from retool just like for the other Google services I use it would save me from getting involved with OAuth2!
Since the auth is implemented for the other services already this feels relatively easy to add, so I hope you can do it!