Contract refactor , Optimization and Using Custom Errors Where ever possible

[aniket866]

Where ? : in contracts

What happened ?: The contract mixes string requires ("Recipient address is zero") with custom errors.

What should be?: Replace all require strings with custom errors (like, error InvalidRecipient(), error PaymentFailed())

Why?: Easy deployment and efficient contract because Strings cost more gas to deploy and execute.
@kumawatkaran523 I have Proposed a fix Please review, #102

[sach2004]

@DengreSarthak @kumawatkaran523 it is a valid issue. the contract already uses custom errors in batch functions but uses string requires everywhere else, it is inconsistent and strings cost more gas, just convert everything to custom errors.