Add IsZero() for address.

types/address.go

@@ -1,4 +1,4 @@
-// Copyright © 2021 - 2023 Attestant Limited.
+// Copyright © 2021 - 2024 Attestant Limited.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -28,6 +28,13 @@ const AddressLength = 20
 // Address is a 20-byte execution layer address.
 type Address [AddressLength]byte
 
+var emptyAddress = Address{}
+
+// IsZero returns true if the address is zero.
+func (a Address) IsZero() bool {
+	return bytes.Equal(a[:], emptyAddress[:])
+}
+
 // String returns the EIP-55 string representation of the address.
 func (a Address) String() string {
 	data := []byte(hex.EncodeToString(a[:]))