Problems Reading Cookies

* Framework version: 1.3.2
* Implementations: Spark

## Scenario
Lambda is fronted by API Gateway which is in turn fronted by cloudfront which is the host of the public vanity URL.

Code is the lambda is looking for a cookie but cannot get get. I assume that this is because it's not getting x-forwarded data? In a similar situation with a ELB running Spring/tomcat we had a similar problem and needed to add the following properties to Spring:

server.tomcat.remote-ip-header=x-forwarded-for
server.tomcat.protocol-header=x-forwarded-proto

I assume there is something like this for Spark? I don't see anything in their documentation?

## Expected behavior
Can read cookies on the vanity domain

## Actual behavior
no cookies :(

## Steps to reproduce
Create the above scenario

Thank You!

Start by tracing how cookies are exposed to the Java Spark implementation when requests pass through API Gateway and CloudFront. Compare the reported vanity-domain scenario with the existing serverless-java-container documentation and request handling behavior; done means cookies can be read in that deployment path.

Written by the indexing model from the issue text.