feat: use error lib

Author: MerlinEgalite

src/Blue.sol

@@ -82,8 +82,8 @@ contract Blue {
     /// @notice It is the owner's responsibility to ensure a fee recipient is set before setting a non-zero fee.
     function setFee(Market calldata market, uint256 newFee) external onlyOwner {
         Id id = market.id();
-        require(lastUpdate[id] != 0, "unknown market");
-        require(newFee <= FEE_CAP, "fee must be <= 20%");
+        require(lastUpdate[id] != 0, Errors.MARKET_NOT_CREATED);
+        require(newFee <= FEE_CAP, Errors.FEE_CAP_EXCEEDED);
         fee[id] = newFee;
     }
 

src/libraries/Errors.sol

@@ -6,6 +6,8 @@ library Errors {
 
     string internal constant LLTV_TOO_HIGH = "LLTV too high";
 
+    string internal constant FEE_CAP_EXCEEDED = "fee must be <= 20%";
+
     string internal constant IRM_NOT_ENABLED = "IRM not enabled";
 
     string internal constant LLTV_NOT_ENABLED = "LLTV not enabled";