Add ability to test client cert configuration in the TestHttpClient

[marklester]

I would like to test some endpoints using client certifications. It looks like api gateway supports it

https://aws.amazon.com/blogs/compute/introducing-mutual-tls-authentication-for-amazon-api-gateway/

maybe do it the way requests does it: https://stackoverflow.com/a/17604076 where you you can pass in a cert tuple to https://github.com/aws/chalice/blob/master/chalice/test.py#L109

and then the info gets added to the lamba event?

[jamesls]

Seems reasonable, sounds like we just need to add those two things you mentioned. Out of curiosity how would you use the info in the lambda event?

[marklester]

The project I am working uses the client identity to look up user attributes from a user store. We use that info to see what groups the user is in and to return records that user is allowed to see.