feat(contracts/core): support user stake delegation

contracts/core/.gas-snapshot

@@ -1,12 +1,12 @@
-Admin_Test:test_pause_unpause() (gas: 33933914)
-Admin_Test:test_pause_unpause_bridge() (gas: 28963667)
-Admin_Test:test_pause_unpause_xcall() (gas: 33887888)
-Admin_Test:test_pause_unpause_xsubmit() (gas: 33887595)
-Admin_Test:test_upgrade() (gas: 37969089)
-AllocPredeploys_Test:test_num_allocs() (gas: 1181319043)
-AllocPredeploys_Test:test_predeploys() (gas: 1181300853)
-AllocPredeploys_Test:test_preinstalls() (gas: 1182017269)
-AllocPredeploys_Test:test_proxies() (gas: 1408944070)
+Admin_Test:test_pause_unpause() (gas: 34028415)
+Admin_Test:test_pause_unpause_bridge() (gas: 29058168)
+Admin_Test:test_pause_unpause_xcall() (gas: 33982389)
+Admin_Test:test_pause_unpause_xsubmit() (gas: 33982096)
+Admin_Test:test_upgrade() (gas: 38063590)
+AllocPredeploys_Test:test_num_allocs() (gas: 1181319931)
+AllocPredeploys_Test:test_predeploys() (gas: 1181301741)
+AllocPredeploys_Test:test_preinstalls() (gas: 1182018157)
+AllocPredeploys_Test:test_proxies() (gas: 1408944958)
 FeeOracleV1_Test:test_bulkSetFeeParams() (gas: 173154)
 FeeOracleV1_Test:test_feeFor() (gas: 122830)
 FeeOracleV1_Test:test_setBaseGasLimit() (gas: 32375)
@@ -150,7 +150,7 @@ Quorum_Test:test_verify_succeeds() (gas: 294059)
 Slashing_Test:test_stub() (gas: 143)
 Slashing_Test:test_unjail() (gas: 54734)
 Staking_Test:test_createValidator() (gas: 145288)
-Staking_Test:test_delegate() (gas: 110001)
+Staking_Test:test_delegate() (gas: 98848)
 Staking_Test:test_stub() (gas: 143)
 Upgrade_Test:test_stub() (gas: 143)
 XAppUpgradeable_Test:test_isXCall() (gas: 148924)

contracts/core/script/admin/StakingPostUpgradeTest.sol

@@ -86,11 +86,16 @@ contract StakingPostUpgradeTest is Test {
 
     function _testDelegate() internal {
         uint256 deposit = staking.MinDelegation();
-        vm.deal(validator, deposit);
+        vm.deal(validator, deposit * 2);
 
         vm.expectEmit();
         emit Staking.Delegate(validator, validator, deposit);
         vm.prank(validator);
         staking.delegate{ value: deposit }(validator);
+
+        vm.expectEmit();
+        emit Staking.Delegate(validator, validator, deposit);
+        vm.prank(validator);
+        staking.delegateFor{ value: deposit }(validator, validator);
     }
 }

contracts/core/src/octane/Staking.sol

@@ -149,19 +149,21 @@ contract Staking is OwnableUpgradeable, EIP712Upgradeable {
     }
 
     /**
-     * @notice Increase your validators self delegation.
-     *         NOTE: Only self delegations to existing validators are currently supported.
-     *         If msg.sender is not a validator, the delegation will be lost.
+     * @notice Delegate tokens to a validator
      * @dev Proxies x/staking.MsgDelegate
+     * @param validator The address of the validator to delegate to
      */
     function delegate(address validator) external payable {
-        require(!isAllowlistEnabled || isAllowedValidator[validator], "Staking: not allowed val");
-        require(msg.value >= MinDelegation, "Staking: insufficient deposit");
-
-        // only support self delegation for now
-        require(msg.sender == validator, "Staking: only self delegation");
+        _delegate(msg.sender, validator);
+    }
 
-        emit Delegate(msg.sender, validator, msg.value);
+    /**
+     * @notice Delegate tokens to a validator for another address
+     * @param delegator The address of the delegator
+     * @param validator The address of the validator to delegate to
+     */
+    function delegateFor(address delegator, address validator) external payable {
+        _delegate(delegator, validator);
     }
 
     //////////////////////////////////////////////////////////////////////////////
@@ -220,4 +222,16 @@ contract Staking is OwnableUpgradeable, EIP712Upgradeable {
         address pubKeyAddress = Secp256k1.pubkeyToAddress(x, y);
         return recovered == pubKeyAddress;
     }
+
+    /**
+     * @notice Delegate tokens to a validator
+     * @param delegator The address of the delegator
+     * @param validator The address of the validator to delegate to
+     */
+    function _delegate(address delegator, address validator) internal {
+        require(!isAllowlistEnabled || isAllowedValidator[validator], "Staking: not allowed val");
+        require(msg.value >= MinDelegation, "Staking: insufficient deposit");
+
+        emit Delegate(delegator, validator, msg.value);
+    }
 }

contracts/core/test/octane/Staking.t.sol

@@ -110,19 +110,13 @@ contract Staking_Test is Test {
 
     function test_delegate() public {
         // requires min delegation
-        address validator = makeAddr("validator");
         uint256 minDelegation = staking.MinDelegation();
 
         vm.deal(validator, minDelegation);
 
         vm.expectRevert("Staking: insufficient deposit");
         staking.delegate{ value: minDelegation - 1 }(validator);
 
-        // requires self-delegation
-        vm.expectRevert("Staking: only self delegation");
-        vm.prank(validator);
-        staking.delegate{ value: minDelegation }(makeAddr("someone else"));
-
         // if allowlist enabled, must be in allowlist
         vm.prank(owner);
         staking.enableAllowlist();