ADD: Add missing ts_in_delta method for StatMsg

CHANGELOG.md

@@ -13,6 +13,8 @@
 - Added new `DBNError` Python exception that's now the primary exception raised by
   `databento_dbn`
 - Improved async performance of decoding DBN files
+- Added `StatMsg::ts_in_delta()` method that returns a `time::Duration` for consistency
+  with other records with a `ts_in_delta` field
 
 ### Breaking changes
 - Changed type of `flags` in `MboMsg`, `TradeMsg`, `Mbp1Msg`, `Mbp10Msg`, and `CbboMsg`

rust/dbn/src/record/methods.rs

@@ -669,6 +669,11 @@ impl StatMsg {
             Error::conversion::<StatUpdateAction>(format!("{:04X}", self.update_action))
         })
     }
+
+    /// Parses the raw `ts_in_delta`—the delta of `ts_recv - ts_exchange_send`—into a duration.
+    pub fn ts_in_delta(&self) -> time::Duration {
+        time::Duration::new(0, self.ts_in_delta)
+    }
 }
 
 impl ErrorMsgV1 {