[#5593] improvement(iceberg): Add final to Iceberg table event members, fix return codes for rename and exists operations (#5594)

### What changes were proposed in this pull request?

1. Add final to Iceberg table-related events and their members.

2. Modify the return codes in `IcebergTableOperations` and
`IcebergTableRenameOperations` to align with the specification, and
update the relevant unit tests.

### Why are the changes needed?

Close: #5593

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Unit test

Author: orenccl

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/rest/IcebergTableOperations.java

@@ -249,7 +249,7 @@ public Response tableExists(
     TableIdentifier tableIdentifier = TableIdentifier.of(icebergNS, table);
     boolean exists = tableOperationDispatcher.tableExists(context, tableIdentifier);
     if (exists) {
-      return IcebergRestUtils.okWithoutContent();
+      return IcebergRestUtils.noContent();
     } else {
       return IcebergRestUtils.notExists();
     }

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/rest/IcebergTableRenameOperations.java

@@ -68,7 +68,7 @@ public Response renameTable(
         renameTableRequest.destination());
     IcebergRequestContext context = new IcebergRequestContext(httpServletRequest(), catalogName);
     tableOperationDispatcher.renameTable(context, renameTableRequest);
-    return IcebergRestUtils.okWithoutContent();
+    return IcebergRestUtils.noContent();
   }
 
   // HTTP request is null in Jersey test, override with a mock request when testing.

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergCreateTableEvent.java

@@ -29,8 +29,8 @@
 @DeveloperApi
 public class IcebergCreateTableEvent extends IcebergTableEvent {
 
-  private CreateTableRequest createTableRequest;
-  private LoadTableResponse loadTableResponse;
+  private final CreateTableRequest createTableRequest;
+  private final LoadTableResponse loadTableResponse;
 
   public IcebergCreateTableEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergCreateTableFailureEvent.java

@@ -27,7 +27,7 @@
 /** Represent a failure event when creating Iceberg table failed. */
 @DeveloperApi
 public class IcebergCreateTableFailureEvent extends IcebergTableFailureEvent {
-  private CreateTableRequest createTableRequest;
+  private final CreateTableRequest createTableRequest;
 
   public IcebergCreateTableFailureEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergCreateTablePreEvent.java

@@ -26,7 +26,7 @@
 /** Represent a pre event before creating Iceberg table. */
 @DeveloperApi
 public class IcebergCreateTablePreEvent extends IcebergTablePreEvent {
-  private CreateTableRequest createTableRequest;
+  private final CreateTableRequest createTableRequest;
 
   public IcebergCreateTablePreEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergDropTableEvent.java

@@ -25,7 +25,7 @@
 /** Represent an event after dropping Iceberg table successfully. */
 @DeveloperApi
 public class IcebergDropTableEvent extends IcebergTableEvent {
-  private boolean purgeRequested;
+  private final boolean purgeRequested;
 
   public IcebergDropTableEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergDropTableFailureEvent.java

@@ -25,7 +25,7 @@
 /** Represent a failure event when dropping Iceberg table failed. */
 @DeveloperApi
 public class IcebergDropTableFailureEvent extends IcebergTableFailureEvent {
-  private boolean purgeRequested;
+  private final boolean purgeRequested;
 
   public IcebergDropTableFailureEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergDropTablePreEvent.java

@@ -25,7 +25,7 @@
 /** Represent a pre event before dropping Iceberg table. */
 @DeveloperApi
 public class IcebergDropTablePreEvent extends IcebergTablePreEvent {
-  private boolean purgeRequested;
+  private final boolean purgeRequested;
 
   public IcebergDropTablePreEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergLoadTableEvent.java

@@ -27,7 +27,7 @@
 /** Represent an event after loading Iceberg table successfully. */
 @DeveloperApi
 public class IcebergLoadTableEvent extends IcebergTableEvent {
-  private LoadTableResponse loadTableResponse;
+  private final LoadTableResponse loadTableResponse;
 
   public IcebergLoadTableEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergRenameTableEvent.java

@@ -27,7 +27,7 @@
 /** Represent an event after rename Iceberg table successfully. */
 @DeveloperApi
 public class IcebergRenameTableEvent extends IcebergTableEvent {
-  private RenameTableRequest renameTableRequest;
+  private final RenameTableRequest renameTableRequest;
 
   public IcebergRenameTableEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergRenameTableFailureEvent.java

@@ -26,7 +26,7 @@
 /** Represent an event when rename Iceberg table failed. */
 @DeveloperApi
 public class IcebergRenameTableFailureEvent extends IcebergTableFailureEvent {
-  private RenameTableRequest renameTableRequest;
+  private final RenameTableRequest renameTableRequest;
 
   public IcebergRenameTableFailureEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergRenameTablePreEvent.java

@@ -26,7 +26,7 @@
 /** Represent an pre event before rename an Iceberg table. */
 @DeveloperApi
 public class IcebergRenameTablePreEvent extends IcebergTablePreEvent {
-  private RenameTableRequest renameTableRequest;
+  private final RenameTableRequest renameTableRequest;
 
   public IcebergRenameTablePreEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergTableExistsEvent.java

@@ -25,7 +25,7 @@
 /** Represent an event after check Iceberg table exists successfully. */
 @DeveloperApi
 public class IcebergTableExistsEvent extends IcebergTableEvent {
-  private boolean isExists;
+  private final boolean isExists;
 
   public IcebergTableExistsEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergUpdateTableEvent.java

@@ -29,8 +29,8 @@
 @DeveloperApi
 public class IcebergUpdateTableEvent extends IcebergTableEvent {
 
-  private UpdateTableRequest updateTableRequest;
-  private LoadTableResponse loadTableResponse;
+  private final UpdateTableRequest updateTableRequest;
+  private final LoadTableResponse loadTableResponse;
 
   public IcebergUpdateTableEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergUpdateTableFailureEvent.java

@@ -27,7 +27,7 @@
 /** Represent a failure event when updating Iceberg table failed. */
 @DeveloperApi
 public class IcebergUpdateTableFailureEvent extends IcebergTableFailureEvent {
-  private UpdateTableRequest updateTableRequest;
+  private final UpdateTableRequest updateTableRequest;
 
   public IcebergUpdateTableFailureEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/listener/api/event/IcebergUpdateTablePreEvent.java

@@ -26,7 +26,7 @@
 /** Represent a pre event before updating Iceberg table. */
 @DeveloperApi
 public class IcebergUpdateTablePreEvent extends IcebergTablePreEvent {
-  private UpdateTableRequest updateTableRequest;
+  private final UpdateTableRequest updateTableRequest;
 
   public IcebergUpdateTablePreEvent(
       IcebergRequestContext icebergRequestContext,

iceberg/iceberg-rest-server/src/test/java/org/apache/gravitino/iceberg/service/rest/TestIcebergTableOperations.java

@@ -210,7 +210,7 @@ void testTableExits() {
 
     verifyCreateTableSucc("exists_foo1");
     dummyEventListener.clearEvent();
-    verifyTableExistsStatusCode("exists_foo1", 200);
+    verifyTableExistsStatusCode("exists_foo1", 204);
     Assertions.assertTrue(dummyEventListener.popPreEvent() instanceof IcebergTableExistsPreEvent);
     postEvent = dummyEventListener.popPostEvent();
     Assertions.assertTrue(postEvent instanceof IcebergTableExistsEvent);
@@ -430,7 +430,7 @@ private void verifyRenameTableSucc(String source, String dest) {
     Response response = doRenameTable(source, dest);
     System.out.println(response);
     System.out.flush();
-    Assertions.assertEquals(Status.OK.getStatusCode(), response.getStatus());
+    Assertions.assertEquals(Status.NO_CONTENT.getStatusCode(), response.getStatus());
   }
 
   private void verifyRenameTableFail(String source, String dest, int status) {