feat: drop peer dependency on @aws-cdk/aws-redshift-alpha (#530)

Fixes #212.

We don't _really_ use the L2 constructs directly, so we add our own
rough type checking logic to replace the one usage we did have but
retain the dev dependency for testing purposes.

For reference, [here's the current L2 `Cluster`
implementation](https://github.com/aws/aws-cdk/blob/v2.146.0/packages/@aws-cdk/aws-redshift-alpha/lib/cluster.ts#L432).

---

_By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license_

.projenrc.ts

@@ -79,10 +79,6 @@ _By submitting this pull request, I confirm that my contribution is made under t
 
 // Experimental modules
 ["@aws-cdk/aws-redshift-alpha"].forEach((dep) => {
-  project.deps.addDependency(
-    `${dep}@^${CDK_VERSION}-alpha.0`,
-    DependencyType.PEER
-  );
   project.deps.addDependency(
     `${dep}@${CDK_VERSION}-alpha.0`,
     DependencyType.DEVENV

README.md

@@ -29,7 +29,6 @@ In your `package.json`:
     "cdk-monitoring-constructs": "^7.0.0",
 
     // peer dependencies of cdk-monitoring-constructs
-    "@aws-cdk/aws-redshift-alpha": "^2.112.0-alpha.0",
     "aws-cdk-lib": "^2.112.0",
     "constructs": "^10.0.5"
 

lib/facade/MonitoringAspect.ts

@@ -1,4 +1,3 @@
-import * as redshift from "@aws-cdk/aws-redshift-alpha";
 import { IAspect } from "aws-cdk-lib";
 import * as apigw from "aws-cdk-lib/aws-apigateway";
 import * as apigwv2 from "aws-cdk-lib/aws-apigatewayv2";
@@ -17,6 +16,7 @@ import * as kinesisfirehose from "aws-cdk-lib/aws-kinesisfirehose";
 import * as lambda from "aws-cdk-lib/aws-lambda";
 import * as opensearch from "aws-cdk-lib/aws-opensearchservice";
 import * as rds from "aws-cdk-lib/aws-rds";
+import { CfnCluster } from "aws-cdk-lib/aws-redshift";
 import * as s3 from "aws-cdk-lib/aws-s3";
 import * as secretsmanager from "aws-cdk-lib/aws-secretsmanager";
 import * as sns from "aws-cdk-lib/aws-sns";
@@ -341,15 +341,24 @@ export class MonitoringAspect implements IAspect {
 
   private monitorRedshift(node: IConstruct) {
     const [isEnabled, props] = this.getMonitoringDetails(this.props.redshift);
-    if (isEnabled && node instanceof redshift.Cluster) {
+    if (isEnabled && this.isProbablyL2RedshiftCluster(node)) {
+      const cfnCluster = (node as any).cluster as CfnCluster;
       this.monitoringFacade.monitorRedshiftCluster({
-        clusterIdentifier: node.clusterName,
-        alarmFriendlyName: node.node.path,
+        clusterIdentifier: cfnCluster.ref,
+        alarmFriendlyName: cfnCluster.node.path,
         ...props,
       });
     }
   }
 
+  private isProbablyL2RedshiftCluster(node: IConstruct): boolean {
+    return (
+      (node as any).cluster instanceof CfnCluster &&
+      !!(node as any).clusterName &&
+      !!(node as any).node?.path
+    );
+  }
+
   private monitorS3(node: IConstruct) {
     const [isEnabled, props] = this.getMonitoringDetails(this.props.s3);
     if (isEnabled && node instanceof s3.Bucket) {