ADD: Add new SystemCode enum UNSUBSCRIBE_ACK

Author: Siddha Kilaru

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.67.0 - Upcoming
+
+### Enhancements
+- Added `UnsubscribeAck` to the `SystemCode` enum for acknowledging unsubscribe requests
+
 ## 0.66.0 - 2026-08-25
 
 ### Enhancements

include/databento/enums.hpp

@@ -700,6 +700,8 @@ enum SystemCode : std::uint8_t {
   // Signals that all records for interval-based schemas have been published for the
   // given timestamp.
   EndOfInterval = 4,
+  // An acknowledgement of an unsubscribe request.
+  UnsubscribeAck = 5,
   // No system code was specified or this record was upgraded from a version 1 struct
   // where
   // the code field didn't exist.

src/enums.cpp

@@ -875,6 +875,9 @@ const char* ToString(SystemCode system_code) {
     case SystemCode::EndOfInterval: {
       return "end_of_interval";
     }
+    case SystemCode::UnsubscribeAck: {
+      return "unsubscribe_ack";
+    }
     case SystemCode::Unset: {
       return "unset";
     }
@@ -1345,6 +1348,9 @@ SystemCode FromString(const std::string& str) {
   if (str == "end_of_interval") {
     return SystemCode::EndOfInterval;
   }
+  if (str == "unsubscribe_ack") {
+    return SystemCode::UnsubscribeAck;
+  }
   if (str == "unset") {
     return SystemCode::Unset;
   }