fix(cfnspec): aws-sam deployment preferences hooks (#19732)

Currently, the `AWS::Serverless::Function.DeploymentPreference.Hooks` property is defined as a list of strings in the cfnspec. However, it should be an object of `{ PreTraffic: '', PostTraffic: '' }` per the spec [here](https://github.com/aws/serverless-application-model/blob/master/versions/2016-10-31.md#deploymentpreference-object).

I updated the tests in `@aws-cdk/aws-sam` to verify the structure.

----

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### Adding new Unconventional Dependencies:

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### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: calabrla

packages/@aws-cdk/aws-sam/test/function.test.ts

@@ -25,3 +25,29 @@ test("correctly chooses a string array from the type unions of the 'policies' pr
     Policies: ['AWSLambdaExecute'],
   });
 });
+
+test('has the correct deployment preference hooks structure', () => {
+  const stack = new cdk.Stack();
+
+  new sam.CfnFunction(stack, 'MyFunction', {
+    deploymentPreference: {
+      enabled: true,
+      type: 'AllAtOnce',
+      hooks: {
+        preTraffic: 'pre-traffic-hook-arn',
+        postTraffic: 'post-traffic-hook-arn',
+      },
+    },
+  });
+
+  Template.fromStack(stack).hasResourceProperties('AWS::Serverless::Function', {
+    DeploymentPreference: {
+      Enabled: true,
+      Type: 'AllAtOnce',
+      Hooks: {
+        PreTraffic: 'pre-traffic-hook-arn',
+        PostTraffic: 'post-traffic-hook-arn',
+      },
+    },
+  });
+});

packages/@aws-cdk/cfnspec/spec-source/specification/100_sam/500_SAM_Serverless_Function_DeploymentPreference_Hooks_patch.json

@@ -0,0 +1,40 @@
+{
+  "PropertyTypes": {
+    "patch": {
+      "description": "Replace AWS::Serverless::Function.DeploymentPreference#Hooks",
+      "operations": [
+        {
+          "op": "replace",
+          "path": "/AWS::Serverless::Function.DeploymentPreference/Properties/Hooks",
+          "value": {
+            "Documentation": "https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#deploymentpreference-object",
+            "Type": "Hooks",
+            "Required": false,
+            "UpdateType": "Immutable"
+          }
+        },
+        {
+          "op": "add",
+          "path": "/AWS::Serverless::Function.Hooks",
+          "value": {
+            "Documentation": "https://github.com/awslabs/serverless-application-model/blob/master/docs/safe_lambda_deployments.rst",
+            "Properties": {
+              "PreTraffic": {
+                "Documentation": "https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#deploymentpreference-object",
+                "Required": false,
+                "PrimitiveType": "String",
+                "UpdateType": "Immutable"
+              },
+              "PostTraffic": {
+                "Documentation": "https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#deploymentpreference-object",
+                "Required": false,
+                "PrimitiveType": "String",
+                "UpdateType": "Immutable"
+              }
+            }
+          }
+        }
+      ]
+    }
+  }
+}