feat(cdk-ops): latest boto3 layer

- Introduces a new CDK construct `LatestBoto3Layer` that provisions a
  Lambda layer containing the latest boto3.
  `lambda/latest-boto3/requirements.txt` lists the modules and versions
  to be packaged as a Lambda layer. The latest boto3 is necessary
  because the default boto3 on the Lambda runtime does not support
  Redshift Serverless.

issue codemonger-io#30

cdk-ops/lambda/latest-boto3/requirements.txt

@@ -0,0 +1,2 @@
+boto3==1.24.75
+botocore==1.27.75

cdk-ops/lib/cdk-ops-stack.ts

@@ -7,6 +7,7 @@ import {
   CodemongerResourceNames,
 } from './codemonger-resources';
 import { ContentsPipeline } from './contents-pipeline';
+import { LatestBoto3Layer } from './latest-boto3-layer';
 
 type Props = StackProps & Readonly<{
   // names of the main codemonger resources.
@@ -22,6 +23,7 @@ export class CdkOpsStack extends Stack {
       'CodemongerResources',
       props.codemongerResourceNames,
     );
+    const latestBoto3 = new LatestBoto3Layer(this, 'LatestBoto3');
     const pipeline = new ContentsPipeline(this, 'ContentsPipeline', {
       codemongerResources,
     });

cdk-ops/lib/latest-boto3-layer.ts

@@ -0,0 +1,28 @@
+import * as path from 'path';
+
+import { aws_lambda as lambda } from 'aws-cdk-lib';
+import { Construct } from 'constructs';
+import { PythonLayerVersion } from '@aws-cdk/aws-lambda-python-alpha';
+
+/** CDK construct that provisions a Lambda layer containing the latest boto3. */
+export class LatestBoto3Layer extends Construct {
+  /** Lambda layer containing the latest boto3. */
+  readonly layer: lambda.ILayerVersion;
+
+  constructor(scope: Construct, id: string) {
+    super(scope, id);
+
+    this.layer = new PythonLayerVersion(this, 'LambdaLayer', {
+      description: 'Lambda layer containing the latest boto3',
+      entry: path.join('lambda', 'latest-boto3'),
+      compatibleRuntimes: [
+        lambda.Runtime.PYTHON_3_8,
+        lambda.Runtime.PYTHON_3_9,
+      ],
+      compatibleArchitectures: [
+        lambda.Architecture.ARM_64,
+        lambda.Architecture.X86_64,
+      ],
+    });
+  }
+}