Create an aws-apigateway.RestAPI resource with mock for CORS header

To set up an AWS API Gateway REST API with a mock for CORS headers, you will need to create a new aws.apigateway.RestApi, define a aws.apigateway.Resource for the OPTIONS method, and configure a aws.apigateway.MethodResponse and aws.apigateway.IntegrationResponse to include the necessary CORS headers. Below is a Pulumi YAML program that specifies these resources:

name: aws-apigateway-cors-mock
runtime: yaml

resources:

  # Create a new REST API
  myApi:
    type: aws:apigateway:RestApi
    properties:
      name: "MyDemoAPI"
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/restapi/

  # Define a root resource ('/') to attach methods
  rootResource:
    type: aws:apigateway:Resource
    properties:
      restApi: ${myApi.id}
      parentId: ${myApi.rootResourceId}
      pathPart: ""
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/resource/

  # Create an OPTIONS method for the root resource to handle CORS preflight requests
  optionsMethod:
    type: aws:apigateway:Method
    properties:
      restApi: ${myApi.id}
      resourceId: ${rootResource.id}
      httpMethod: "OPTIONS"
      authorization: "NONE"
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/method/

  # Set the mock integration for OPTIONS method
  mockIntegration:
    type: aws:apigateway:Integration
    properties:
      restApi: ${myApi.id}
      resourceId: ${rootResource.id}
      httpMethod: ${optionsMethod.httpMethod}
      type: "MOCK" # Indicates this is a mock integration
      requestTemplates:
        "application/json": "{\"statusCode\": 200}" # A simple request template
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/integration/

  # Define the method response for 200
  methodResponse200:
    type: aws:apigateway:MethodResponse
    properties:
      restApi: ${myApi.id}
      resourceId: ${rootResource.id}
      httpMethod: ${optionsMethod.httpMethod}
      statusCode: "200"
      responseModels: {"application/json": "Empty"}
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/methodresponse/

  # Define the integration response to include CORS headers
  integrationResponse200:
    type: aws:apigateway:IntegrationResponse
    properties:
      restApi: ${myApi.id}
      resourceId: ${rootResource.id}
      httpMethod: ${optionsMethod.httpMethod}
      statusCode: "200"
      responseTemplates: {"application/json": ""}
      responseParameters:
        "method.response.header.Access-Control-Allow-Headers": "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token,Access-Control-Allow-Origin'"
        "method.response.header.Access-Control-Allow-Methods": "'DELETE,GET,HEAD,OPTIONS,PATCH,POST,PUT'"
        "method.response.header.Access-Control-Allow-Origin": "'*'"
    # This is the link to the resource's documentation:
    # https://www.pulumi.com/registry/packages/aws/api-docs/apigateway/integrationresponse/

This program sets up a REST API with a mock integration that responds to OPTIONS preflight requests for CORS by providing the necessary headers such as Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers.

Remember that after setting up the API Gateway resources, you will also need to deploy the API for it to become active. This usually involves creating an aws.apigateway.Deployment and possibly linking it to a aws.apigateway.Stage. This part is not included in the provided code, but you should take it as the next step to actually deploy and utilize your API.