Feature Request: Add DEBUG mode to the API Gateway Event Handler

[michaelbrewer]

Is your feature request related to a problem? Please describe.

When there was an error while developing my initial lambda, i would like to be able to see more information when debug mode is turned on.

Describe the solution you'd like

Add a DEBUG mode or feature flag, that should never used in production, which can do the following:

1. Pretty print the json responses
2. Get more context when there is an error
3. Relax rules for setting up CORS

Describe alternatives you've considered

For debugging errors, you can also look at the lambda logs, but i would be nice to allow for the end user to get more context event before accessing the logs.

Additional context

[michaelbrewer]

@heitorlessa i have a PR up for this

[heitorlessa]

Released in 1.18.0