feat: HubRestricted base contract added

contracts/core/FollowNFT.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.8.15;
+pragma solidity 0.8.15;
 
 import {IFollowNFT} from '../interfaces/IFollowNFT.sol';
 import {IFollowModule} from '../interfaces/IFollowModule.sol';
@@ -10,7 +10,7 @@ import {Errors} from '../libraries/Errors.sol';
 import {Events} from '../libraries/Events.sol';
 import {DataTypes} from '../libraries/DataTypes.sol';
 import {LensNFTBase} from './base/LensNFTBase.sol';
-import {ModuleBase} from './modules/ModuleBase.sol';
+import {HubRestricted} from './base/HubRestricted.sol';
 import {IERC721} from '@openzeppelin/contracts/token/ERC721/IERC721.sol';
 import {ERC721Time} from './base/ERC721Time.sol';
 import '../libraries/Constants.sol';
@@ -35,7 +35,7 @@ struct FollowData {
     uint96 followTimestamp;
 }
 
-contract FollowNFT is ModuleBase, LensNFTBase, IFollowNFT {
+contract FollowNFT is HubRestricted, LensNFTBase, IFollowNFT {
     bytes32 internal constant DELEGATE_BY_SIG_TYPEHASH =
         keccak256(
             'DelegateBySig(address delegator,address delegatee,uint256 nonce,uint256 deadline)'
@@ -57,7 +57,7 @@ contract FollowNFT is ModuleBase, LensNFTBase, IFollowNFT {
     mapping(uint256 => uint256) internal _approvedToFollowByFollowerId;
     mapping(uint256 => address) internal _approvedToSetFollowerByFollowId;
 
-    constructor(address hub) ModuleBase(hub) {
+    constructor(address hub) HubRestricted(hub) {
         _initialized = true;
     }
 
@@ -534,7 +534,7 @@ contract FollowNFT is ModuleBase, LensNFTBase, IFollowNFT {
     }
 
     function _delegate(address delegator, address delegatee) internal {
-        uint256 delegatorBalance = balanceOf(delegator);
+        uint256 delegatorBalance = balanceOf(delegator); // TODO: This is only getting the wrapped tokens balance
         address previousDelegate = _delegates[delegator];
         _delegates[delegator] = delegatee;
         _moveDelegate(previousDelegate, delegatee, delegatorBalance);

contracts/core/base/HubRestricted.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity 0.8.15;
+
+import {Errors} from '../../libraries/Errors.sol';
+import {Events} from '../../libraries/Events.sol';
+
+/**
+ * @title HubRestricted
+ * @author Lens Protocol
+ *
+ * @notice This abstract contract adds a public `HUB` immutable field, validations when setting it, as well
+ * as an `onlyHub` modifier, to inherit from contracts that have functions restricted to be only called by the Lens hub.
+ */
+abstract contract HubRestricted {
+    address public immutable HUB;
+
+    modifier onlyHub() {
+        if (msg.sender != HUB) {
+            revert Errors.NotHub();
+        }
+        _;
+    }
+
+    constructor(address hub) {
+        if (hub == address(0)) {
+            revert Errors.InitParamsInvalid();
+        }
+        HUB = hub;
+    }
+}

contracts/core/modules/ModuleBase.sol

@@ -4,25 +4,17 @@ pragma solidity 0.8.15;
 
 import {Errors} from '../../libraries/Errors.sol';
 import {Events} from '../../libraries/Events.sol';
+import {HubRestricted} from '../base/HubRestricted.sol';
 
 /**
  * @title ModuleBase
  * @author Lens Protocol
  *
- * @notice This abstract contract adds a public `HUB` immutable to inheriting modules, as well as an
- * `onlyHub` modifier.
+ * @notice This contract fires an event at construction, to be inherited by other modules, in addition to the
+ * HubRestricted contract features.
  */
-abstract contract ModuleBase {
-    address public immutable HUB;
-
-    modifier onlyHub() {
-        if (msg.sender != HUB) revert Errors.NotHub();
-        _;
-    }
-
-    constructor(address hub) {
-        if (hub == address(0)) revert Errors.InitParamsInvalid();
-        HUB = hub;
+abstract contract ModuleBase is HubRestricted {
+    constructor(address hub) HubRestricted(hub) {
         emit Events.ModuleBaseConstructed(hub, block.timestamp);
     }
 }