Function cellar_core::generate_app_key

pub fn generate_app_key(
    passphrase: &str, 
    aux: &AuxiliaryData, 
    info: &[u8], 
    key_type: KeyType
) -> Result<Vec<u8>, CellarError>

generate application key based on user's passphrase, auxilliary data (salt and seed), as well as the app info as an entropy.