Function processERC20ApprovalPayload

processERC20ApprovalPayload(
payload: ERC20ApprovalGasSponsorPayload,
extensionInfo: ERC20ApprovalGasSponsorExtensionInfo,
): ERC20ApprovalGasSponsorValidationResult
Processes and validates an ERC-20 approval payload for the facilitator.

Combines extraction validation with approve() function selector verification. Checks that the signed transaction data contains the correct approve() selector and that the approval amount matches the declared amount.
Parameters
- payload: ERC20ApprovalGasSponsorPayload
  The ERC-20 approval gas sponsor payload
- extensionInfo: ERC20ApprovalGasSponsorExtensionInfo
  The server's gas sponsor extension info
Returns ERC20ApprovalGasSponsorValidationResult
Validation result
Example
```
const result = processERC20ApprovalPayload(payload, extensionInfo);
if (result.valid) {
  // Safe to broadcast the approval tx and settle
}
```
- Defined in extensions/src/erc20-approval-gas-sponsoring/facilitator.ts:88