Depracate incorrect grpc stream proxy implementation

Author: alex268

core/src/main/java/tech/ydb/core/impl/call/ProxyReadStream.java

@@ -11,6 +11,7 @@
  * @param <BaseR> type of origin stream message
  * @param <DestR> new stream message type
  */
+@Deprecated
 public class ProxyReadStream<BaseR, DestR> implements GrpcReadStream<DestR> {
     public interface MessageFunctor<BaseR, DestR> {
         void apply(BaseR message, CompletableFuture<Status> promise, Observer<DestR> observer);
@@ -25,18 +26,19 @@ public ProxyReadStream(GrpcReadStream<BaseR> origin, MessageFunctor<BaseR, DestR
         this.functor = functor;
     }
 
+    protected void onClose(Status status, Throwable th) {
+        // promise may be completed by functor and in that case this code will be ignored
+        if (th != null) {
+            future.completeExceptionally(th);
+        }
+        if (status != null) {
+            future.complete(status);
+        }
+    }
+
     @Override
     public CompletableFuture<Status> start(Observer<DestR> observer) {
-        origin.start(response -> functor.apply(response, future, observer)).whenComplete((status, th) -> {
-            // promise may be completed by functor and in that case this code will be ignored
-            if (th != null) {
-                future.completeExceptionally(th);
-            }
-            if (status != null) {
-                future.complete(status);
-            }
-        });
-
+        origin.start(response -> functor.apply(response, future, observer)).whenComplete(this::onClose);
         return future;
     }