Function history_subdir_for 

fn history_subdir_for(
    acct: &IdentityAccount,
    dir: &Path,
) -> Option<&'static str>

The conversation-history subdirectory name for an OAuth config dir: from the account’s provider, or else from the dir’s own name, which is the provider’s auth_dir_name (identities/<account>/<auth_dir_name>/).