fix(river-api): revoke user token before logout

[simonvadee]

Fixes

Fixes #561

Description

We need to call the oprovider/o/revoke_token route to invalidate the access token and then remove the user from the oprovider session by redirecting the browser to /oprovider/admin/logout/.

Definition of Done

• [x] I followed the Arkhn Code Book (I swear!).
• [ ] I have written tests for the code I added or updated.
• [x] I have updated the documentation according to my changes.
• [x] I have updated the deployment configuration if needed.

Tests

Tested on dev. Too hard to e2e test (sorry).