pub fn prepare_erc20_approval(
token_address: &str,
owner_address: &str,
spender_address: &str,
amount_minor_units: u128,
) -> Result<PreparedErc20Approval, SettlementError>pub fn prepare_erc20_approval(
token_address: &str,
owner_address: &str,
spender_address: &str,
amount_minor_units: u128,
) -> Result<PreparedErc20Approval, SettlementError>