Function indy_sys::payments::indy_build_payment_req

#[no_mangle]
pub unsafe extern "C" fn indy_build_payment_req(
    command_handle: CommandHandle, 
    wallet_handle: WalletHandle, 
    submitter_did: CString, 
    inputs_json: CString, 
    outputs_json: CString, 
    extra: CString, 
    cb: Option<ResponseStringStringCB>
) -> Error