perf: refactor index registry to use internal functions for modifier (#…

…269)

* fix: deprecated struct field for earning receiver

* perf: move modifier logic to internal function

src/IndexRegistry.sol

@@ -12,7 +12,7 @@ contract IndexRegistry is IndexRegistryStorage {
 
     /// @notice when applied to a function, only allows the RegistryCoordinator to call it
     modifier onlyRegistryCoordinator() {
-        require(msg.sender == address(registryCoordinator), "IndexRegistry.onlyRegistryCoordinator: caller is not the registry coordinator");
+        _checkRegistryCoordinator();
         _;
     }
 
@@ -340,4 +340,8 @@ contract IndexRegistry is IndexRegistryStorage {
     function totalOperatorsForQuorum(uint8 quorumNumber) external view returns (uint32){
         return _latestQuorumUpdate(quorumNumber).numOperators;
     }
+
+    function _checkRegistryCoordinator() internal view {
+        require(msg.sender == address(registryCoordinator), "IndexRegistry.onlyRegistryCoordinator: caller is not the registry coordinator");
+    }
 }