Update changelogs from fern repo (#4420)

Author: fern-support

fern/products/sdks/overview/csharp/changelog/2026-03-20.mdx

@@ -1,3 +1,14 @@
+## 2.43.0
+**`(feat):`** Add per-message deflate compression support (RFC 7692) for WebSocket connections.
+A new `EnableCompression` option on the generated WebSocket Options class enables
+`WebSocketDeflateOptions` via `ClientWebSocketOptions.DangerousDeflateOptions`.
+This can significantly reduce bandwidth for text-heavy (JSON) WebSocket APIs.
+Warning: Do not use compression when sending data containing secrets
+(CRIME/BREACH vulnerability).
+See https://learn.microsoft.com/dotnet/api/system.net.websockets.clientwebsocketoptions.dangerousdeflateoptions
+for details.
+
+
 ## 2.42.0
 **`(feat):`** Add support for HTTP/2 WebSockets via `SocketsHttpHandler`. A new `HttpInvoker`
 property on the WebSocket Options class allows passing an `HttpMessageInvoker` to