I'm trying to get a refresh token for Google through Oauth.io but I'm having trouble finding the endpoint to send the code to. I'm using C# so I can't use the server-side SDK. I've also looked at Getting refresh tokens from Google with OAuth.io but that answer doesn't help me get the actual refresh token. I've looked at their server-side flow documentation which tells me I can get my refresh token at /auth/access_token but when looking at the web API documentation I don't see that endpoint listed.
I've also looked at their example here and I don't see the endpoint they use listed on the API documentation either. It also doesn't say which key/secret to use with that request - is it the one listed for my OAuth.io app, or is it the one for my provider (in this case Google)?
Any help going forward would be greatly appreciated.