I'm trying to do an APEX Callout to a OAuth 2.0 secured REST API
I want to use something to manage the security token rather than write APEX code to do it. And according to this that's what Named Credentials are for. Specifically this passage:
Salesforce manages all authentication for callouts that specify a named credential as the callout endpoint so that you don’t have to. You can also skip remote site settings, which are otherwise required for callouts to external sites, for the site defined in the named credential.
The problem I have is I'm trying to use an Auth Provider but there's no OAuth 2.0 option so I'm using OpenID. Which if I understand correctly rides on OAuth 2.0. I'm not sure what the "Redirect URI" should be from the PandaDoc API side. I'm using the "Callback URL" but it's not working.
I have the whole flow working in Postman from the Collection PandaDoc publishes. They also have a video showing the Postman setup. I'm able to use the builtin Postman OAuth 2.0 Authorization to get the Access Token and make successful calls to the PandaDoc API.
In my case I'm calling PandaDoc API but this would be useful for anyone calling out from Salesforce to any OAuth 2.0 secured API. I didn't find any good examples of how to make an Apex Callout to an OAuth 2.0 REST API.