feat(rds): add clusterArn property to IServerlessCluster (aws#10741)

This PR adds a property `clusterArn` to `IServerlessCluster`. This simplifies the usage of the Data API which requires passing the ARN of the cluster in Data API calls.

closes aws#10736


----

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

packages/@aws-cdk/aws-rds/lib/serverless-cluster.ts

@@ -1,7 +1,7 @@
 import * as ec2 from '@aws-cdk/aws-ec2';
 import * as kms from '@aws-cdk/aws-kms';
 import * as secretsmanager from '@aws-cdk/aws-secretsmanager';
-import { Resource, Duration, Token, Annotations, RemovalPolicy, IResource } from '@aws-cdk/core';
+import { Resource, Duration, Token, Annotations, RemovalPolicy, IResource, Stack } from '@aws-cdk/core';
 import { Construct } from 'constructs';
 import { IClusterEngine } from './cluster-engine';
 import { DatabaseSecret } from './database-secret';
@@ -23,6 +23,11 @@ export interface IServerlessCluster extends IResource, ec2.IConnectable, secrets
    */
   readonly clusterIdentifier: string;
 
+  /**
+   * The ARN of the cluster
+   */
+  readonly clusterArn: string;
+
   /**
    * The endpoint to use for read/write operations
    * @attribute EndpointAddress,EndpointPort
@@ -282,6 +287,18 @@ abstract class ServerlessClusterBase extends Resource implements IServerlessClus
    */
   public abstract readonly connections: ec2.Connections;
 
+  /**
+   * The ARN of the cluster
+   */
+  public get clusterArn(): string {
+    return Stack.of(this).formatArn({
+      service: 'rds',
+      resource: 'cluster',
+      sep: ':',
+      resourceName: this.clusterIdentifier,
+    });
+  }
+
   /**
    * Renders the secret attachment target specifications.
    */

packages/@aws-cdk/aws-rds/test/test.serverless-cluster.ts

@@ -617,6 +617,37 @@ export = {
 
     test.done();
   },
+
+  'check that clusterArn property works'(test: Test) {
+    // GIVEN
+    const stack = testStack();
+    const vpc = ec2.Vpc.fromLookup(stack, 'VPC', { isDefault: true });
+    const cluster = new ServerlessCluster(stack, 'Database', {
+      engine: DatabaseClusterEngine.AURORA_MYSQL,
+      vpc,
+    });
+    const exportName = 'DbCluterArn';
+
+    // WHEN
+    new cdk.CfnOutput(stack, exportName, {
+      exportName,
+      value: cluster.clusterArn,
+    });
+
+    // THEN
+    test.deepEqual(stack.resolve(cluster.clusterArn), {
+      'Fn::Join': [
+        '',
+        [
+          'arn:',
+          { Ref: 'AWS::Partition' },
+          ':rds:us-test-1:12345:cluster:',
+          { Ref: 'DatabaseB269D8BB' },
+        ],
+      ],
+    });
+    test.done();
+  },
 };
 
 function testStack() {