[keycloak-user] Differnentiate Login Error for Disabled Account (Version 3.4.3 Final)

When a disabled user tries to login, he gets an error 400 Bad Request (error: "invalid_grant", error_description: "Account disabled"). However, in my project, there are multiple reasons for a user to be disabled, which are distinguishable by certain attributes I set to the user. My goal is to create a Keycloak extension to customize the response based on those attributes, so that a different error message can be shown to the user. Providing a different value error_description would be a solution. My question is: Is it possible to intercept that error message before it is sent to the client, and if so, what kind of SPI do I need to write to handle that? I am using Keycloak version 3.4.3 Final. Regards, Patrick Bucher