feat: use osm in source adapter

Signed-off-by: Reinis Martinsons <reinis@umaproject.org>

src/adapters/makerdao/ChronicleSourceOracleAdapter.sol

@@ -2,24 +2,24 @@
 pragma solidity 0.8.17;
 
 import "../../interfaces/IBaseOracleAdapter.sol";
-import "../../interfaces/chronicle/IMedian.sol";
+import "../../interfaces/chronicle/IOSM.sol";
 
 contract ChronicleSourceOracleAdapter is IBaseOracleAdapter {
-    IMedian public source;
+    IOSM public source;
 
     // MakerDAO performs decimal conversion in collateral adapter contracts, so all oracle prices are expected to have
     // 18 decimals.
     uint8 public constant decimals = 18;
 
-    constructor(IMedian _source) {
+    constructor(IOSM _source) {
         source = _source;
     }
 
     function latestAnswer() public view override returns (int256) {
-        return int256((source.read() * (10 ** 18)) / (10 ** decimals));
+        return int256((uint(source.read()) * (10 ** 18)) / (10 ** decimals));
     }
 
     function latestTimestamp() public view override returns (uint256) {
-        return source.age();
+        return source.zzz();
     }
 }

src/interfaces/chronicle/IOSM.sol

@@ -11,7 +11,7 @@ interface IOSM {
     // function src() external view returns (address); // Address of source oracle.
 
     // function hop() external view returns (uint16); // Oracle delay in seconds.
-    // function zzz() external view returns (uint64); // Start of current period timestamp.
+    function zzz() external view returns (uint64); // Start of period timestamp when the price was last updated.
 
     // function bud(address _addr) external view returns (uint256); // Whitelisted contracts, set by an auth
 
@@ -28,7 +28,7 @@ interface IOSM {
 
     function peek() external view returns (bytes32, bool); // Return current price and if valid (whitelisted)
     // function peep() external view returns (bytes32, bool); // Return the next price and if valid (whitelisted)
-    // function read() external view returns (bytes32); // Return current price, only if valid (whitelisted)
+    function read() external view returns (bytes32); // Return current price, only if valid (whitelisted)
 
     // function kiss(address a) external; // Add address to whitelist (auth)
     // function diss(address a) external; // Remove address from whitelist (auth)