feat: add CDK diff PR workflow and update workflow actions to v5

Author: dannysteenman

.gitattributes

@@ -2,7 +2,7 @@ import { awscdk, JsonFile, TextFile } from 'projen';
 import { DependabotScheduleInterval } from 'projen/lib/github';
 import { NodePackageManager } from 'projen/lib/javascript';
 import { IndentStyle, QuoteStyle, Semicolons, TrailingCommas } from 'projen/lib/javascript/biome/biome-config';
-import { createCdkDeploymentWorkflows } from './src/bin/cicd-helper';
+import { createCdkDeploymentWorkflows, createCdkDiffPrWorkflow } from './src/bin/cicd-helper';
 import { addCdkActionTask, type Environment, type EnvironmentConfig } from './src/bin/env-helper';
 
 // Set the minimum node version for AWS CDK and the GitHub actions workflow
@@ -195,6 +195,16 @@ if (project.github) {
       orderedEnvironments,
     );
   }
+
+  // Create CDK diff PR workflow (once, using the highest environment)
+  createCdkDiffPrWorkflow(
+    project.github,
+    environmentConfigs[environmentConfigs.length - 1].accountId, // Uses the account that should be deployed to last (usually production)
+    awsRegion,
+    githubRole,
+    nodeVersion,
+    orderedEnvironments,
+  );
 }
 
 project.synth();

.github/workflows/cdk-deploy-production.yml

@@ -63,6 +63,7 @@ Welcome to the starting line of your next AWS CDK project. This repository is cr
 - 🧹 **Preconfigured TypeScript Excellence**: Hit the ground running with pre-set compiler options in [tsconfig.json](./tsconfig.json), ensuring your code is clean, efficient, and error-free from the start.
 - 📏 **Best Practice Linting & Formatting**: Adopt coding best practices effortlessly with a pre-configured Biome setup [biome.jsonc](./biome.jsonc), maintaining high code quality and consistency.
 - 💻 **Branch-based Deployments**: Deploy multiple CDK stacks to the same AWS environments based on the Git branch. This enables you to easily test changes when multiple developers work on the same code base.
+- 🔍 **Automated CDK Diff on PRs**: Automatically runs `cdk diff` on pull requests to the main branch and posts the infrastructure changes as a comment. This allows you to validate your infrastructure changes before merging. Powered by our custom-built [AWS CDK Diff PR Commenter](https://github.com/marketplace/actions/aws-cdk-diff-pr-commenter) GitHub Action.
 - 📦 **Automated Dependency Management**: Dependabot creates grouped PRs, with auto-approval for passing checks using `hmarr/auto-approve-action@v4`, streamlining updates while maintaining project stability.
 
 ## Setup Guide