Function indy_sys::payments::indy_build_set_txn_fees_req

#[no_mangle]
pub unsafe extern "C" fn indy_build_set_txn_fees_req(
    command_handle: Handle, 
    wallet_handle: Handle, 
    submitter_did: CString, 
    payment_method: CString, 
    fees_json: CString, 
    cb: Option<ResponseStringCB>
) -> Error