Improve "Disable" Login Functionality and Consistency

Currently the disable login have a few missing:

1. It is common that we need to give a reason why a user is disabled. So we need to:
- When disable from portal, allow users to choose a reason optionally (the UI better show last N most frequent reason for disable)
- When user try to login with a disabled account, show the reason
2. Terminlogy, is it "Disable" or "Blocked"? it seems used inter-changable else where, e.g. In translation `error-blocked-user` `error-disabled-user`

Start by tracing the portal flow for disabling a user and the login handling for disabled accounts, then inspect the translation keys error-blocked-user and error-disabled-user. Done means an optional disable reason can be selected, the reason is shown during login, and the Disable/Blocked terminology is made consistent.

Written by the indexing model from the issue text.