feat: Implement Serializable interface for rich text classes

src/main/java/com/contentful/java/cda/rich/CDARichBlock.java

@@ -1,12 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
 import java.util.LinkedList;
 import java.util.List;
 
 /**
  * A collection of several nodes.
  */
-public class CDARichBlock extends CDARichNode {
+public class CDARichBlock extends CDARichNode implements Serializable {
   final List<CDARichNode> content = new LinkedList<>();
 
   /**

src/main/java/com/contentful/java/cda/rich/CDARichDocument.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * The base of a rich text field, containing all the other nodes.
  */
-public class CDARichDocument extends CDARichBlock {
+public class CDARichDocument extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichEmbeddedBlock.java

@@ -1,11 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * This node is an inline link to a CDAEntry
  *
  * @see com.contentful.java.cda.CDAEntry
  */
-public class CDARichEmbeddedBlock extends CDARichHyperLink {
+public class CDARichEmbeddedBlock extends CDARichHyperLink implements Serializable {
   /**
    * Create a link pointing to a CDAEntry.
    *

src/main/java/com/contentful/java/cda/rich/CDARichEmbeddedInline.java

@@ -1,11 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * This node is an inline link to a CDAEntry
  *
  * @see com.contentful.java.cda.CDAEntry
  */
-public class CDARichEmbeddedInline extends CDARichHyperLink {
+public class CDARichEmbeddedInline extends CDARichHyperLink implements Serializable {
   /**
    * Create a link pointing to a CDAEntry.
    *

src/main/java/com/contentful/java/cda/rich/CDARichHeading.java

@@ -1,11 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * Defines a headline of the text.
  * <p>
  * Can have an arbitrary level assigned, but useful probably between 1 and 6.
  */
-public class CDARichHeading extends CDARichBlock {
+public class CDARichHeading extends CDARichBlock implements Serializable {
   private final int level;
 
   /**

src/main/java/com/contentful/java/cda/rich/CDARichHorizontalRule.java

@@ -1,9 +1,11 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A node representing a division, called a horizontal rule.
  */
-public class CDARichHorizontalRule extends CDARichNode {
+public class CDARichHorizontalRule extends CDARichNode implements Serializable {
   /**
    * Construct this node.
    */

src/main/java/com/contentful/java/cda/rich/CDARichHyperLink.java

@@ -1,9 +1,11 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * This block represents a link to a website.
  */
-public class CDARichHyperLink extends CDARichBlock {
+public class CDARichHyperLink extends CDARichBlock implements Serializable {
   Object data;
 
   /**

src/main/java/com/contentful/java/cda/rich/CDARichList.java

@@ -1,9 +1,11 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * Parent class for all list classes
  */
-public class CDARichList extends CDARichBlock {
+public class CDARichList extends CDARichBlock implements Serializable {
   final CharSequence decoration;
 
   /**

src/main/java/com/contentful/java/cda/rich/CDARichListItem.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A block representing an item inside a list.
  */
-public class CDARichListItem extends  CDARichBlock {
+public class CDARichListItem extends  CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichMark.java

@@ -1,11 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * How to draw a given text.
  * <p>
  * Subclasses are used for further differentiation.
  */
-public class CDARichMark {
+public class CDARichMark implements Serializable {
 
   public CDARichMark(String type) {
     this.type = type;

src/main/java/com/contentful/java/cda/rich/CDARichNode.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A leaf node of the rich text hierarchy.
  */
-public class CDARichNode {
+public class CDARichNode implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichOrderedList.java

@@ -1,9 +1,11 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A list of elements, ordered by number.
  */
-public class CDARichOrderedList extends CDARichList {
+public class CDARichOrderedList extends CDARichList implements Serializable {
   /**
    * Create a list with numbers.
    */

src/main/java/com/contentful/java/cda/rich/CDARichParagraph.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A paragraph of nodes, usually rendered together.
  */
-public class CDARichParagraph extends CDARichBlock {
+public class CDARichParagraph extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichQuote.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A block of nodes rendered as a direct quote.
  */
-public class CDARichQuote extends CDARichBlock {
+public class CDARichQuote extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichTable.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A paragraph of nodes, usually rendered together.
  */
-public class CDARichTable extends CDARichBlock {
+public class CDARichTable extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichTableCell.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A paragraph of nodes, usually rendered together.
  */
-public class CDARichTableCell extends CDARichBlock {
+public class CDARichTableCell extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichTableHeaderCell.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A paragraph of nodes, usually rendered together.
  */
-public class CDARichTableHeaderCell extends CDARichBlock {
+public class CDARichTableHeaderCell extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichTableRow.java

@@ -1,7 +1,9 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * A paragraph of nodes, usually rendered together.
  */
-public class CDARichTableRow extends CDARichBlock {
+public class CDARichTableRow extends CDARichBlock implements Serializable {
 }

src/main/java/com/contentful/java/cda/rich/CDARichText.java

@@ -1,12 +1,13 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 
 /**
  * A leaf element of the rich text node graph: Render a given text with the given markings.
  */
-public class CDARichText extends CDARichNode {
+public class CDARichText extends CDARichNode implements Serializable {
   private final List<CDARichMark> marks = new ArrayList<>();
   private final CharSequence text;
 

src/main/java/com/contentful/java/cda/rich/CDARichUnorderedList.java

@@ -1,9 +1,11 @@
 package com.contentful.java.cda.rich;
 
+import java.io.Serializable;
+
 /**
  * Representation of a block of unordered items.
  */
-public class CDARichUnorderedList extends CDARichList {
+public class CDARichUnorderedList extends CDARichList implements Serializable {
   /**
    * Create a list with bullet points.
    */