I would much prefer to directly use their REST API, but Retool has no current integration with it and I could not get an authorization workflow to run.
Can Retool add support for Cloudinary as an integrated resource?
The trick here would seem to be in "signing" every request through the API -- essentially hashing a sorted subset of POST body parameters and then adding the hash AS another body parameter before firing the request.
Retool's REST resource does not appear to have a way to post-process each request in order to sign them automatically.
As you mentioned, Retool currently doesn't support including scripts as part of a custom auth flow, though it is a known request and being tracked here. We also have a separate existing internal request for a Cloudinary integration and if that gets picked up we can let you know here as well!
At the moment, the solution we have for running auth that requires scripting is to do so in the app itself so that you can make use of JS queries or preloaded JS. You can also store values in localStorage. So, conceivably, you could have your users log in through a dedicated app that stores the signed token in localStorage, and then reference that in subsequent queries made in other apps.
I am in the same position, it would be really great if retool started to integrate with Cloudinary.
Ideally it would be great if retool started to integrate with other service providers, so that we as builders and users could include advanced functionality with out having to build and maintain the integration.