[mysql] Add a method to get MySqlSourceConfigFactory from MySqlSource (apache#648)

Author: Tuple

flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/MySqlSource.java

@@ -75,7 +75,7 @@
  *
  * <pre>{@code
  * MySqlSource
- *     .<RowData>builder()
+ *     .<String>builder()
  *     .hostname("localhost")
  *     .port(3306)
  *     .databaseList("mydb")
@@ -117,6 +117,10 @@ public static <T> MySqlSourceBuilder<T> builder() {
         this.deserializationSchema = deserializationSchema;
     }
 
+    public MySqlSourceConfigFactory getConfigFactory() {
+        return configFactory;
+    }
+
     @Override
     public Boundedness getBoundedness() {
         return Boundedness.CONTINUOUS_UNBOUNDED;