This is a rebased version of #4796 from @laardee 👍 🥇 🙌

What did you implement:

Closes #3944

Adds support for Lambda@Edge via pure CloudFormation. Thanks again to @laardee who jumped in to work on an initial implementation for this!

How did you implement it:

Compile all the necessary CloudFormation resources (CloudFront / Versioned Lambda function, etc.) to add support for Lambda@Edge.

Todos:

• Retain Lambda Functions to avoid errors on Stack removals
• Log info that functions have to be removed by hand when removing stack

How can we verify it:

Create a new serverless service and replace the handler.js and serverless.yml code with the following snippets:

// handler.js
module.exports.cloudfront = (event, context, callback) => {
  const response = event.Records[0].cf.response;
  const headers = response.headers;

  headers['x-serverless-time'] = [{ key: 'x-serverless-time', value: Date.now().toString() }];

  return callback(null, response);
};

service: test-${self:custom.idx}

provider:
  name: aws
  runtime: nodejs10.x
  versionFunctions: false

custom:
  idx: 0

functions:
  hello:
    handler: handler.hello
    events:
      - cloudFront:
          eventType: viewer-response
          origin: https://serverless.com/framework/docs

Deploy the service (this could take a couple of minutes (~10 - 20mins)). After that you can access the CloudFront distribution URL which is printed in your console (you can also use serverless info). This should open up the Serverless Framework docs page.

Inspect the headers (e.g. using this guide if you're running Chrome). You should see the x-serverless-time header which was added by the Lambda@Edge function.

Once validated you might want to remove the stack. Note the info message about the necessary manual Lambda@Edge function removals which is logged on the console.

Todos:

Note: Run npm run test-ci to run all validation checks on proposed changes

• Write tests and confirm existing functionality is not broken.
  Validate via npm test
• Write documentation
• Ensure there are no lint errors.
  Validate via npm run lint-updated
  Note: Some reported issues can be automatically fixed by running npm run lint:fix
• Ensure introduced changes match Prettier formatting.
  Validate via npm run prettier-check-updated
  Note: All reported issues can be automatically fixed by running npm run prettify-updated
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO