Function create_contract_and_fetch_invoice 

pub(crate) async fn create_contract_and_fetch_invoice(
    federation_id: FederationId,
    recipient_pk: PublicKey,
    aggregate_pk: AggregatePublicKey,
    gateways: Vec<SafeUrl>,
    amount: u64,
    expiry_secs: u32,
    gateway_conn: &RealGatewayConnection,
) -> Result<(SafeUrl, Bolt11Invoice)>