feat(neptune): add copyTagsToSnapshot property to the DatabaseCluster Construct (#30092)

### Issue # (if applicable)

Closes #30087 

### Reason for this change
As described in the issue.



### Description of changes
Add copyTagsToSnapshot property to the DatabaseCluster Construct.


### Description of how you validated changes
Add both unit tests and integ tests.


### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: mazyu36

packages/@aws-cdk/aws-neptune-alpha/README.md

@@ -25,7 +25,7 @@ import * as neptune from '@aws-cdk/aws-neptune-alpha';
 
 ## Starting a Neptune Database
 
-To set up a Neptune database, define a `DatabaseCluster`. You must always launch a database in a VPC. 
+To set up a Neptune database, define a `DatabaseCluster`. You must always launch a database in a VPC.
 
 ```ts
 const cluster = new neptune.DatabaseCluster(this, 'Database', {
@@ -126,9 +126,9 @@ const replica1 = new neptune.DatabaseInstance(this, 'Instance', {
 
 ## Automatic minor version upgrades
 
-By setting `autoMinorVersionUpgrade` to true, Neptune will automatically update 
-the engine of the entire cluster to the latest minor version after a stabilization 
-window of 2 to 3 weeks. 
+By setting `autoMinorVersionUpgrade` to true, Neptune will automatically update
+the engine of the entire cluster to the latest minor version after a stabilization
+window of 2 to 3 weeks.
 
 ```ts
 new neptune.DatabaseCluster(this, 'Cluster', {
@@ -184,9 +184,21 @@ instance.metric('SparqlRequestsPerSec') // instance-level SparqlErrors metric
 
 For more details on the available metrics, refer to https://docs.aws.amazon.com/neptune/latest/userguide/cw-metrics.html
 
+## Copy tags to snapshot
+
+By setting `copyTagsToSnapshot` to true, all tags of the cluster are copied to the snapshots when they are created.
+
+```ts
+const cluster = new neptune.DatabaseCluster(this, 'Database', {
+  vpc,
+  instanceType: neptune.InstanceType.R5_LARGE,
+  copyTagsToSnapshot: true  // whether to save the cluster tags when creating the snapshot.
+});
+```
+
 ## Neptune Serverless
 
-You can configure a Neptune Serverless cluster using the dedicated instance type along with the 
+You can configure a Neptune Serverless cluster using the dedicated instance type along with the
 `serverlessScalingConfiguration` property.
 
 > Visit [Using Amazon Neptune Serverless](https://docs.aws.amazon.com/neptune/latest/userguide/neptune-serverless-using.html) for more details.

packages/@aws-cdk/aws-neptune-alpha/lib/cluster.ts

@@ -89,7 +89,7 @@ export class EngineVersion {
    * Constructor for specifying a custom engine version
    * @param version the engine version of Neptune
    */
-  public constructor(public readonly version: string) {}
+  public constructor(public readonly version: string) { }
 }
 
 /**
@@ -109,7 +109,7 @@ export class LogType {
    * Constructor for specifying a custom log type
    * @param value the log type
    */
-  public constructor(public readonly value: string) {}
+  public constructor(public readonly value: string) { }
 }
 
 export interface ServerlessScalingConfiguration {
@@ -325,6 +325,13 @@ export interface DatabaseClusterProps {
    * @default - required if instanceType is db.serverless
    */
   readonly serverlessScalingConfiguration?: ServerlessScalingConfiguration;
+
+  /**
+   * Whether to copy tags to the snapshot when a snapshot is created.
+   *
+   * @default - false
+   */
+  readonly copyTagsToSnapshot?: boolean;
 }
 
 /**
@@ -620,6 +627,8 @@ export class DatabaseCluster extends DatabaseClusterBase implements IDatabaseClu
       enableCloudwatchLogsExports: props.cloudwatchLogsExports?.map(logType => logType.value),
       storageEncrypted,
       serverlessScalingConfiguration: props.serverlessScalingConfiguration,
+      // Tags
+      copyTagsToSnapshot: props.copyTagsToSnapshot,
     });
 
     cluster.applyRemovalPolicy(props.removalPolicy, {

packages/@aws-cdk/aws-neptune-alpha/test/cluster.test.ts

@@ -879,6 +879,40 @@ describe('DatabaseCluster', () => {
       RetentionInDays: 30,
     });
   });
+
+  test('copyTagsToSnapshot is not set by default', () => {
+    // GIVEN
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    // WHEN
+    new DatabaseCluster(stack, 'Database', {
+      vpc,
+      instanceType: InstanceType.R5_LARGE,
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::Neptune::DBCluster', {
+      CopyTagsToSnapshot: Match.absent(),
+    });
+  });
+
+  test.each([false, true])('cluster with copyTagsToSnapshot set', (value) => {
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    // WHEN
+    new DatabaseCluster(stack, 'Database', {
+      vpc,
+      instanceType: InstanceType.R5_LARGE,
+      copyTagsToSnapshot: value,
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::Neptune::DBCluster', {
+      CopyTagsToSnapshot: value,
+    });
+  });
 });
 
 function testStack() {