Make MongoWriteException Serializable

Implement Serializable for WriteError. This is the only non-serializable field in MongoWriteException. Exceptions are supposed to be serializable.

driver-core/src/main/com/mongodb/WriteError.java

@@ -18,14 +18,18 @@
 
 import org.bson.BsonDocument;
 
+import java.io.Serializable;
+
 import static com.mongodb.assertions.Assertions.notNull;
 
 /**
  * Represents the details of a write error , e.g. a duplicate key error
  *
  * @since 3.0
  */
-public class WriteError {
+public class WriteError implements Serializable {
+
+    private static final long serialVersionUID = 5582035144266419294L;
     private final int code;
     private final String message;
     private final BsonDocument details;

driver-core/src/test/unit/com/mongodb/MongoWriteExceptionTest.java

@@ -19,14 +19,23 @@
 
 import org.bson.BsonDocument;
 import org.bson.BsonInt32;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.nio.file.Path;
 import java.util.Collections;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class MongoWriteExceptionTest {
 
+    @TempDir
+    Path tempDir;
+
     @Test
     public void testExceptionProperties() {
         WriteError writeError = new WriteError(11000, "Duplicate key", new BsonDocument("x", new BsonInt32(1)));
@@ -38,4 +47,23 @@ public void testExceptionProperties() {
         assertEquals(writeError.getCode(), e.getCode());
         assertEquals(writeError, e.getError());
     }
+
+    @Test
+    public void testExceptionSerializable() throws Exception {
+        WriteError writeError = new WriteError(11000, "Duplicate key", new BsonDocument("x", new BsonInt32(1)));
+        MongoWriteException writeException = new MongoWriteException(writeError, new ServerAddress("host1"), Collections.emptySet());
+
+
+        Path tempPath = tempDir.resolve("testFile");
+        try (FileOutputStream fileOutputStream = new FileOutputStream(tempPath.toFile());
+             ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream)) {
+            objectOutputStream.writeObject(writeException);
+        }
+
+        try (FileInputStream fileInputStream = new FileInputStream(tempPath.toFile());
+             ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream)) {
+            MongoWriteException deserializedException = (MongoWriteException) objectInputStream.readObject();
+            assertEquals(writeException.getError(), deserializedException.getError());
+        }
+    }
 }