Function parse_existing_local_user_id 

pub(crate) async fn parse_existing_local_user_id(
    services: &Services,
    user_id: &str,
) -> Result<OwnedUserId>

Parses user ID as our local user holding an account, deactivated or not.

A command writing for an absent user would create the account or leave state behind for whoever registers the name later, so it refuses here.