Rebase and refactor ApiKeyRequired feature

[brettstack]

This feature (https://github.com/awslabs/serverless-application-model/pull/444/files) was merged into a feature branch (https://github.com/awslabs/serverless-application-model/tree/feat/auth) while we worked on the design for Auth as a whole. Now that we have that, we should rebase this change and refactor it to use the Auth property so that we can get this merged into develop.

[jlhood]

@tylersouthwick Would you be willing to do this? We'd love to get this out into an official release!

[cfbarbero]

This has come up at my company so I'd like to jump in on this.

Here is what I'm proposing to do:
Update the Auth property to include a new sub-property ApiKeyRequired: <boolean>. This will be supported on both the Api Auth Method and the Function Auth Method. The function level specification will override the API level.

For example:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: API Gateway with AWS IAM Authorizer
Resources:
  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      Auth:
        ApiKeyRequired: true
        DefaultAuthorizer: AWS_IAM
        InvokeRole: CALLER_CREDENTIALS

  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: .
      Handler: index.handler
      Runtime: nodejs8.10
      Events:
        GetRoot:
          Type: Api
          Properties:
            RestApiId: !Ref MyApi
            Path: /
            Method: get
            # This is a public endpoint
            Auth:
              Authorizer: NONE
              ApiKeyRequired: false
        GetOther:
          Type: Api
          Properties:
            RestApiId: !Ref MyApi
            Path: /other
            Method: get

Outputs:
  ApiURL:
    Description: "API URL"
Value: !Sub 'https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/'

[jlhood]

@cfbarbero Awesome!! What you're proposing looks like what we're expecting. Looking forward to seeing your PR! Feel free to reach out on this issue if you have questions.

[jlhood]

Pending v1.14.0 release

[ShreyaGangishetty]

Closing this issue as this is released in v1.14.0