fix: fix typing on core middy handler

[markcarroll]

What does this implement/fix? Explain your changes.

With current Typescript definition it is not possible to locally execute the handler function, either from a local file to debug, or from unit tests, without getting a Typescript error:

This expression is not callable.
  Type 'MiddyfiedHandler<APIGatewayProxyEvent, APIGatewayProxyResult, Error>' has no call signatures.

I believe the issue is that the Typescript definition of the MiddyfiedHandler does not extend the Lambda Handler so is not a callable function.

Fix is to add LambdaHandler to the MiddyfiedHandler interface definition.

Does this close any currently open issues?

closes #628

Any relevant logs, error output, etc?

Any other comments?

Looking for someone else to validate this fix. Since it is only typing, it does not affect core functionality.

Where has this been tested?

Node.js Versions: v14.15.5

Middy Versions: 2.0.0.beta.0

AWS SDK Versions: v2/v3

Todo list

[ ] Feature/Fix fully implemented
[ ] Added tests
[ ] Updated relevant documentation
[ ] Updated relevant examples

[lmammino]

Thanks for reporting this!

Do you think there is any way we can add a test for this in our typing tests?

[markcarroll]

The reason it broke for me in the first place was when I tried to execute the handler as a callable function. It should be as simple as trying to call it as Lambda runtime would. I don’t have a window to look at it right now, but I will take a look when I get a chance.