add ERC20BaseInternal#_decreaseAllowance function for generic holder

Author: ItsNickBarry

contracts/token/ERC20/base/ERC20BaseInternal.sol

@@ -68,6 +68,26 @@ abstract contract ERC20BaseInternal is IERC20BaseInternal {
         return true;
     }
 
+    /**
+     * @notice decrease spend amount granted by holder to spender
+     * @param holder address on whose behalf tokens may be spent
+     * @param spender address whose allowance to decrease
+     * @param amount quantity by which to decrease allowance
+     */
+    function _decreaseAllowance(
+        address holder,
+        address spender,
+        uint256 amount
+    ) internal {
+        uint256 allowance = _allowance(holder, spender);
+
+        require(allowance >= amount, 'ERC20: insufficient allowance');
+
+        unchecked {
+            _approve(holder, spender, allowance - amount);
+        }
+    }
+
     /**
      * @notice mint tokens for given account
      * @param account recipient of minted tokens
@@ -151,16 +171,7 @@ abstract contract ERC20BaseInternal is IERC20BaseInternal {
         address recipient,
         uint256 amount
     ) internal virtual returns (bool) {
-        uint256 allowance = _allowance(holder, msg.sender);
-
-        require(
-            allowance >= amount,
-            'ERC20: transfer amount exceeds allowance'
-        );
-
-        unchecked {
-            _approve(holder, msg.sender, allowance - amount);
-        }
+        _decreaseAllowance(holder, msg.sender, amount);
 
         _transfer(holder, recipient, amount);
 

contracts/token/ERC20/extended/ERC20ExtendedInternal.sol

@@ -47,12 +47,8 @@ abstract contract ERC20ExtendedInternal is
         virtual
         returns (bool)
     {
-        uint256 allowance = _allowance(msg.sender, spender);
-
-        require(amount <= allowance, 'ERC20Extended: insufficient allowance');
+        _decreaseAllowance(msg.sender, spender, amount);
 
-        unchecked {
-            return _approve(msg.sender, spender, allowance - amount);
-        }
+        return true;
     }
 }