feat(appsync): add L2 constuct for AppSync

packages/@aws-cdk/aws-appsync/README.md

@@ -16,3 +16,94 @@
 <!--END STABILITY BANNER-->
 
 This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aws-cdk) project.
+
+## Usage Example
+
+Given the following GraphQL schema file `schema.graphql`:
+
+```graphql
+type Customer {
+    id: String!
+    name: String!
+}
+
+input SaveCustomerInput {
+    name: String!
+}
+
+type Query {
+    getCustomers: [Customer]
+    getCustomer(id: String): Customer
+}
+
+type Mutation {
+    addCustomer(customer: SaveCustomerInput!): Customer
+    saveCustomer(id: String!, customer: SaveCustomerInput!): Customer
+    removeCustomer(id: String!): Customer
+}
+```
+
+the following CDK app snippet will create a complete CRUD AppSync API:
+
+```ts
+export class ApiStack extends Stack {
+  constructor(scope: Construct, id: string) {
+    super(scope, id);
+
+    const userPool = new UserPool(this, 'UserPool', {
+      signInType: SignInType.USERNAME,
+    });
+
+    const api = new GraphQLApi(this, 'Api', {
+      name: `demoapi`,
+      logConfig: {
+        fieldLogLevel: FieldLogLevel.ALL,
+      },
+      userPoolConfig: {
+        userPool,
+        defaultAction: UserPoolDefaultAction.ALLOW,
+      },
+      schemaDefinitionFile: './schema.graphql',
+    });
+
+    const customerTable = new Table(this, 'CustomerTable', {
+      billingMode: BillingMode.PAY_PER_REQUEST,
+      partitionKey: {
+        name: 'id',
+        type: AttributeType.STRING,
+      },
+    });
+    const customerDS = api.addDynamoDbDataSource('Customer', 'The customer data source', customerTable);
+    customerDS.createResolver({
+      typeName: 'Query',
+      fieldName: 'getCustomers',
+      requestMappingTemplate: MappingTemplate.dynamoDbScanTable(),
+      responseMappingTemplate: MappingTemplate.dynamoDbResultList(),
+    });
+    customerDS.createResolver({
+      typeName: 'Query',
+      fieldName: 'getCustomer',
+      requestMappingTemplate: MappingTemplate.dynamoDbGetItem('id', 'id'),
+      responseMappingTemplate: MappingTemplate.dynamoDbResultItem(),
+    });
+    customerDS.createResolver({
+      typeName: 'Mutation',
+      fieldName: 'addCustomer',
+      requestMappingTemplate: MappingTemplate.dynamoDbPutItem('id', 'customer'),
+      responseMappingTemplate: MappingTemplate.dynamoDbResultItem(),
+    });
+    customerDS.createResolver({
+      typeName: 'Mutation',
+      fieldName: 'saveCustomer',
+      requestMappingTemplate: MappingTemplate.dynamoDbPutItem('id', 'customer', 'id'),
+      responseMappingTemplate: MappingTemplate.dynamoDbResultItem(),
+    });
+    customerDS.createResolver({
+      typeName: 'Mutation',
+      fieldName: 'removeCustomer',
+      requestMappingTemplate: MappingTemplate.dynamoDbDeleteItem('id', 'id'),
+      responseMappingTemplate: MappingTemplate.dynamoDbResultItem(),
+    });
+  }
+}
+```