How to revoke Guardian access token?
The documentation: https://hexdocs.pm/guardian/Guardian.Token.Jwt.html#revoke/4 says that it should be implemented with GuardianDB callback, but I have no idea how it should be.
By default you cannot revoke guardian tokens, because they are entirely maintained on the client side. You need to track them somehow on the server side if you want to be able to revoke them. This has the disadvantage of requiring a check against this storage every time you verify a token. You can either implement this yourself, or use https://github.com/ueberauth/guardian_db - see their readme for details.