Human readable description of why the code action is currently disabled, if it is disabled.
This is displayed in the code actions UI. When non-null, this indicates that the code action cannot currently be applied.
Clients should follow the following guidelines regarding disabled code actions:
action menus.
the user request a more specific type of code action, such as
refactorings.
a disabled code actions are returned, the client should show the user
an error message with `reason` in the editor.
3.16.0