Address comments

Author: mzitnik

flink-connector-clickhouse-base/src/main/java/org/apache/flink/connector/clickhouse/convertor/ClickHouseConvertor.java

@@ -12,6 +12,7 @@
 
 public class ClickHouseConvertor<InputT> implements ElementConverter<InputT, ClickHousePayload> {
     private static final Logger LOG = LoggerFactory.getLogger(ClickHouseConvertor.class);
+    private static final long serialVersionUID = 1L;
 
     POJOConvertor<InputT> pojoConvertor = null;
     enum Types {

flink-connector-clickhouse-base/src/main/java/org/apache/flink/connector/clickhouse/exception/RetriableException.java

@@ -1,6 +1,8 @@
 package org.apache.flink.connector.clickhouse.exception;
 
 public class RetriableException extends FlinkWriteException {
+    private static final long serialVersionUID = 1L;
+
     public RetriableException(String message) {
         super(message);
     }

flink-connector-clickhouse-base/src/main/java/org/apache/flink/connector/clickhouse/sink/ClickHouseAsyncSink.java

@@ -16,6 +16,7 @@
 import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Objects;
 
 public class ClickHouseAsyncSink<InputT> extends AsyncSinkBase<InputT, ClickHousePayload> {
     private static final Logger LOG = LoggerFactory.getLogger(ClickHouseAsyncSink.class);
@@ -41,7 +42,7 @@ public ClickHouseAsyncSink(
               maxTimeInBufferMS,
               maxRecordSizeInByte);
 
-        this.clickHouseClientConfig = clickHouseClientConfig;
+        this.clickHouseClientConfig = Objects.requireNonNull(clickHouseClientConfig, "ClickHouse config cannot be null");;
     }
 
     public void setClickHouseFormat(ClickHouseFormat clickHouseFormat) {

flink-connector-clickhouse-base/src/main/java/org/apache/flink/connector/clickhouse/sink/ClickHouseClientConfig.java

@@ -9,6 +9,7 @@
 
 public class ClickHouseClientConfig implements Serializable {
     private static final Logger LOG = LoggerFactory.getLogger(ClickHouseClientConfig.class);
+    private static final long serialVersionUID = 1L;
 
     private final String url;
     private final String username;

flink-connector-clickhouse-base/src/test/java/org/apache/flink/connector/clickhouse/sink/ClickHouseSinkTests.java

@@ -226,8 +226,6 @@ void SimplePOJODataTest() throws Exception {
                 clickHouseClientConfig
         );
 
-        simplePOJOSink.setClickHouseFormat(ClickHouseFormat.RowBinary);
-
         List<SimplePOJO> simplePOJOList = new ArrayList<>();
         for (int i = 0; i < EXPECTED_ROWS; i++) {
             simplePOJOList.add(new SimplePOJO(i));