feat: Using @Serial (#2806)

retry/src/main/java/com/iluwatar/retry/BusinessException.java

@@ -24,6 +24,8 @@
  */
 package com.iluwatar.retry;
 
+import java.io.Serial;
+
 /**
  * The top-most type in our exception hierarchy that signifies that an unexpected error condition
  * occurred. Its use is reserved as a "catch-all" for cases where no other subtype captures the
@@ -33,6 +35,7 @@ package com.iluwatar.retry;
  * @author George Aristy (george.aristy@gmail.com)
  */
 public class BusinessException extends Exception {
+  @Serial
   private static final long serialVersionUID = 6235833142062144336L;
 
   /**

retry/src/main/java/com/iluwatar/retry/DatabaseNotAvailableException.java

@@ -24,12 +24,15 @@
  */
 package com.iluwatar.retry;
 
+import java.io.Serial;
+
 /**
  * Catastrophic error indicating that we have lost connection to our database.
  *
  * @author George Aristy (george.aristy@gmail.com)
  */
 public final class DatabaseNotAvailableException extends BusinessException {
+  @Serial
   private static final long serialVersionUID = -3750769625095997799L;
 
   /**