Gas Optimizations

[code423n4]

gas

#1 Using custom error
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanFacilitator.sol#L81-L86
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanFacilitator.sol#L118
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanFacilitator.sol#L121
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanFacilitator.sol#L171-L172
Declared by error statement, and using revert statement to throw the error message. This method is better for gas improvement than just using long string

#2 Tight var packing in Loan struct
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/interfaces/INFTLoanFacilitator.sol#L6-L16
By arranging the variables, it is possible to minimize the number of slots used within a contract's storage and therefore reduce deployment costs. Address var are 20 bytes size and bool are 1, there's a slot here that can get saved by moving them closer to an address.
Change to:

    struct Loan {
        uint16 perAnumInterestRate;
        uint32 durationSeconds;
        uint40 lastAccumulatedTimestamp;
        address collateralContractAddress;
        address loanAssetContractAddress;
        bool closed;
        uint128 accumulatedInterest;
        uint128 loanAmount;
        uint256 collateralTokenId;
    }

#3 Better using != than > or <
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanFacilitator.sol#L321
!= is more efficient than < or > for gas optimization

#4 Using calldata to store string var parameter
https://github.com/code-423n4/2022-04-backed/blob/main/contracts/NFTLoanTicket.sol#L21-L22
Using calldata instead of memory can save gas