feat: support for operator specific delegators

contracts/contracts/validator-registry/middleware/MevCommitMiddleware.sol

@@ -613,7 +613,8 @@ contract MevCommitMiddleware is IMevCommitMiddleware, MevCommitMiddlewareStorage
         IEntity delegator = IEntity(IVault(vault).delegator());
         if (delegator.TYPE() == _FULL_RESTAKE_DELEGATOR_TYPE) {
             revert FullRestakeDelegatorNotSupported(vault);
-        } else if (delegator.TYPE() != _NETWORK_RESTAKE_DELEGATOR_TYPE) {
+        // Only two delegator types are supported, network-restake and operator-specific.
+        } else if (delegator.TYPE() != _NETWORK_RESTAKE_DELEGATOR_TYPE && delegator.TYPE() != _OPERATOR_SPECIFIC_DELEGATOR_TYPE) {
             revert UnknownDelegatorType(vault, delegator.TYPE());
         }
 

contracts/contracts/validator-registry/middleware/MevCommitMiddlewareStorage.sol

@@ -16,6 +16,9 @@ abstract contract MevCommitMiddlewareStorage {
     /// @notice Enum TYPE for Symbiotic core FullRestakeDelegator.
     uint64 internal constant _FULL_RESTAKE_DELEGATOR_TYPE = 1;
 
+    /// @notice Enum TYPE for Symbiotic core OperatorSpecificDelegator.
+    uint64 internal constant _OPERATOR_SPECIFIC_DELEGATOR_TYPE = 2;
+
     /// @notice Enum TYPE for Symbiotic core InstantSlasher.
     uint64 internal constant _INSTANT_SLASHER_TYPE = 0;
 

contracts/contracts/validator-registry/middleware/README.md

@@ -16,7 +16,7 @@ For L1 validators to be *opted-in to mev-commit*, some collateral stake must be
 
 Operators for the mev-commit network are responsible for bulk registering groups of L1 validator pubkeys to an associated vault. Every registered validator is represented by restaked collateral from a single Vault and Operator. Each Vault’s total collateral can be split up to secure/represent many validators in groups**.**
 
-Our network middleware contract requires any Vault registering with the contract to have a delegator of the `NetworkRestakeDelegator` type. `FullRestakeDelegator` is disallowed due to its ability for vaults to reuse stake within the same network to multiple Operators. In other words, a single instance of `slashAmount` vault collateral can only be used to secure a single validator.
+Our network middleware contract requires any Vault registering with the contract to have a delegator of the `NetworkRestakeDelegator` type or `OperatorSpecificDelegator` type. `FullRestakeDelegator` is disallowed due to its ability for vaults to reuse stake within the same network to multiple Operators. In other words, a single instance of `slashAmount` vault collateral can only be used to secure a single validator, through a single Operator. Vaults are still able to split their slashable collateral across multiple Operators.
 
 # Steps for validator opt-in via symbiotic
 

contracts/test/validator-registry/middleware/MevCommitMiddlewareTest.sol

@@ -583,9 +583,10 @@ contract MevCommitMiddlewareTest is Test {
         mevCommitMiddleware.registerVaults(vaults, slashAmounts);
 
         uint64 networkRestakeDelegatorType = 0;
+        uint64 operatorSpecificDelegatorType = 2;
 
         mockDelegator1.setType(networkRestakeDelegatorType);
-        mockDelegator2.setType(networkRestakeDelegatorType);
+        mockDelegator2.setType(operatorSpecificDelegatorType);
 
         vm.prank(owner);
         vm.expectRevert(