feat(contracts/core): support user stake delegation (#2681)

Added _initial_ support for user stake delegation to the `Staking`
contract, and updated related Go. I also added support for delegating on
behalf of other users. The omni CLI delegate command was only updated
for the new delegate function interface, so CLI still only supports
self-delegation, for now.

It has yet to be determined what contract changes, if any, are necessary
for unstaking. This contract should not be upgraded yet until the entire
scope is known.

issue: #567

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();