add oracle permissions to contract

src/AstriaOracle.sol

@@ -4,6 +4,9 @@ pragma solidity ^0.8.21;
 // Core oracle contract for Astria's native oracle.
 // This contract stores the price data for every currency pair supported by the oracle.
 contract AstriaOracle {
+    // the `astriaOracleSenderAddress` built into the astria-geth node
+    address public immutable ORACLE;
+
     // mapping of block number to mapping of hash of the currency pair string to its price data
     mapping(uint256 => mapping(bytes32 => PriceData)) public priceData;
 
@@ -13,16 +16,21 @@ contract AstriaOracle {
     // block number of the latest price data update
     uint256 public latestBlockNumber;
 
+    modifier onlyOracle() {
+        require(msg.sender == ORACLE, "AstriaOracle: only oracle can update");
+        _;
+    }
+
     struct PriceData {
         uint128 price;
         uint256 timestamp;
     }
 
-    function setDecimals(bytes32 _currencyPair, uint8 _decimals) public {
+    function setDecimals(bytes32 _currencyPair, uint8 _decimals) external onlyOracle {
         decimals[_currencyPair] = _decimals;
     }
 
-    function updatePriceData(bytes32[] memory _currencyPairs, uint128[] memory _prices) public {
+    function updatePriceData(bytes32[] memory _currencyPairs, uint128[] memory _prices) external onlyOracle {
         require(_currencyPairs.length == _prices.length, "currency pair and price length mismatch");
         latestBlockNumber = block.number;
         for (uint256 i = 0; i < _currencyPairs.length; i++) {