fix(waf-v2): include Region dimension if specified (#317)

The metrics specifically have a `Region` dimension when using a regional Web ACL (as opposed to a global Cloudfront one that lacks that dimension).

Also explicitly specify a `name` for the test resources, as it seems like `CfnWebACL` doesn't return a `name` if you don't set it.

---

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

Author: Eugene Cheung

API.md

@@ -6,8 +6,12 @@ const MetricNamespace = "AWS/WAFV2";
 const AllRulesDimensionValue = "ALL";
 
 export interface WafV2MetricFactoryProps {
-  readonly region?: string;
   readonly acl: CfnWebACL;
+
+  /**
+   * Required if acl has a "REGIONAL" scope.
+   */
+  readonly region?: string;
 }
 
 /**
@@ -22,6 +26,7 @@ export class WafV2MetricFactory {
     this.dimensions = {
       Rule: AllRulesDimensionValue,
       WebACL: props.acl.name,
+      ...(props.region && { Region: props.region }),
     };
   }
 

lib/monitoring/aws-wafv2/WafV2MetricFactory.ts

@@ -9,6 +9,7 @@ import { TestMonitoringScope } from "../TestMonitoringScope";
 test("snapshot test: no alarms", () => {
   const stack = new Stack();
   const acl = new CfnWebACL(stack, "DummyAcl", {
+    name: "DummyAclName",
     defaultAction: { allow: {} },
     scope: "REGIONAL",
     visibilityConfig: {
@@ -20,7 +21,7 @@ test("snapshot test: no alarms", () => {
 
   const scope = new TestMonitoringScope(stack, "Scope");
 
-  const monitoring = new WafV2Monitoring(scope, { acl });
+  const monitoring = new WafV2Monitoring(scope, { acl, region: "us-east-1" });
 
   addMonitoringDashboardsToStack(stack, monitoring);
   expect(Template.fromStack(stack)).toMatchSnapshot();
@@ -29,8 +30,9 @@ test("snapshot test: no alarms", () => {
 test("snapshot test: all alarms", () => {
   const stack = new Stack();
   const acl = new CfnWebACL(stack, "DummyAcl", {
+    name: "DummyAclName",
     defaultAction: { allow: {} },
-    scope: "REGIONAL",
+    scope: "CLOUDFRONT",
     visibilityConfig: {
       sampledRequestsEnabled: true,
       cloudWatchMetricsEnabled: true,