SDK clean-ups

[Ang-dot]

PR changes:

• add evaluator rejection reason
• DRY hydrate job function
• implement payableAmount in SDK level

[JohnsonChin1009]

Performed two main testings for netPayableAmount calculation in SDK level.

USDC (6 Decimals)

Since USDC has a maximum of 6 decimals, the edge case that I aimed to test is if the calculated service fee is < 1μ it should default to 1μ (in this case, 0.005 will be 0.0000005 which translates to 0.5μ).

• Input: Use fund_transfer with Pepechad, transfer 0.005 USDC to <target_address>
• Expected Output: target_address gets 0.000001 USDC, <agent> gets 0.004999 USDC
• Actual Output: target_address gets 0.005 USDC, <agent> gets 0 USDC

This contradicts with the design where any service fee that is <1μ should always default to 1μ

*Important to note that μ in solidity only supports integer and not values such as 0.5

Next Steps: Identify the issue and where to fix it by @Ang-dot

Ether (18 Decimals)

For tokens that have 18 decimals, the function that truncates to decimals is actually making the calculation lose accuracy because it only truncates to 6 decimals as shown below:

// acpFare.ts
constructor(fareAmount: number, fare: Fare) {
  const truncateTo6Decimals = (input: string): number => {
    const [intPart, decPart = ""] = input.split(".");

    if (decPart === "") {
      return parseFloat(intPart);
    }

    const truncated = decPart.slice(0, 6).padEnd(6, "0");

    return parseFloat(`${intPart}.${truncated}`);
  };

  super(fare.formatAmount(truncateTo6Decimals(fareAmount.toString())), fare);
}

Hence, I've implemented a fix for it by letting it truncate to take in the decimal from the Fare object

constructor(fareAmount: number, fare: Fare) {
  const truncateToTokenDecimals = (input: string, decimals: number): number => {
    const [intPart, decPart = ""] = input.split(".");

    if (decPart === "") {
      return parseFloat(intPart);
    }

    const truncated = decPart.slice(0, decimals);

    return parseFloat(`${intPart}.${truncated}`);
  };

  super(fare.formatAmount(truncateToTokenDecimals(fareAmount.toString(), fare.decimals)), fare);
}

Next Steps: Review the code and make sure that it is backward compatible with USDC (tested out by @JohnsonChin1009, but needs someone to help review)
Results

	truncateTo6Decimals	truncateToTokenDecimals
Input	0.003456789123	0.003456789123
Truncated Output	0.003456	0.003456789123