fix(cdk): narrow dlqAlarm public type to cloudwatch.IAlarm

Consumers only need addAlarmAction (defined on IAlarm); exposing the
concrete Alarm class leaks the full mutable surface unnecessarily.

Author: nizar-lahlali

cdk/src/constructs/approval-metrics-publisher-consumer.ts

@@ -85,7 +85,7 @@ export interface ApprovalMetricsPublisherConsumerProps {
 export class ApprovalMetricsPublisherConsumer extends Construct {
   public readonly fn: lambda.NodejsFunction;
   public readonly dlq: sqs.Queue;
-  public readonly dlqAlarm: cloudwatch.Alarm;
+  public readonly dlqAlarm: cloudwatch.IAlarm;
 
   constructor(scope: Construct, id: string, props: ApprovalMetricsPublisherConsumerProps) {
     super(scope, id);

cdk/src/constructs/fanout-consumer.ts

@@ -107,7 +107,7 @@ export interface FanOutConsumerProps {
 export class FanOutConsumer extends Construct {
   public readonly fn: lambda.NodejsFunction;
   public readonly dlq: sqs.Queue;
-  public readonly dlqAlarm: cloudwatch.Alarm;
+  public readonly dlqAlarm: cloudwatch.IAlarm;
 
   constructor(scope: Construct, id: string, props: FanOutConsumerProps) {
     super(scope, id);