Contract is missing from IsValid() and bytes() in delegate

[wyuinche]

Expected Behavior

contract account must be validated in delegate-item.

Actual Behavior

No validation for contract in IsValid(byte[]).
No byte slice of contract in Bytes().

mitum-nft/nft/collection/delegate_item.go

Line 60 in 7cb90dc

func (it DelegateItem) IsValid([]byte) error {

mitum-nft/nft/collection/delegate_item.go

Line 70 in 7cb90dc

func (it DelegateItem) Bytes() []byte {

Steps to Reproduce the Problem

Omit

Specifications

• commit; 7cb90dc
• os; macos ventura
• go version; go1.19