Unknown enum variants removed from server (#1398)

The server must have the most up to date variants and the unknown enum
variant should not be used. Clients are generated with it because they
might not have the most recent model and the server might return
an unknown variant to them.

Closes #1187

Signed-off-by: Daniele Ahmed <ahmeddan@amazon.de>

Co-authored-by: Daniele Ahmed <ahmeddan@amazon.de>
Co-authored-by: david-perez <d@vidp.dev>
Co-authored-by: Matteo Bigoi <1781140+crisidev@users.noreply.github.com>