Make new classes serializable

This is required for compatibility with pdfDebug

Author: IdamkinI

kernel/src/main/java/com/itextpdf/kernel/ProductInfo.java

@@ -43,11 +43,15 @@ This file is part of the iText (R) project.
  */
 package com.itextpdf.kernel;
 
+import java.io.Serializable;
+
 /**
  * Describes an iText 7 add on. An add on should register itself to a PdfDocument object if it
  * wants to be included in the debugging information.
  */
-public class ProductInfo {
+public class ProductInfo implements Serializable {
+    private static final long serialVersionUID = 2410734474798313936L;
+
     private String name;
     private int major;
     private int minor;

kernel/src/main/java/com/itextpdf/kernel/pdf/FingerPrint.java

@@ -45,6 +45,7 @@ This file is part of the iText (R) project.
 
 import com.itextpdf.kernel.ProductInfo;
 
+import java.io.Serializable;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.Set;
@@ -54,7 +55,8 @@ This file is part of the iText (R) project.
  * was involved in the creation of a certain PDF file. This information can then be used to log to the
  * logger or to the file.
  */
-public class FingerPrint {
+public class FingerPrint implements Serializable {
+    private static final long serialVersionUID = 1378019250639368423L;
 
     private Set<ProductInfo> productInfoSet;