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!

先追蹤當請求經過 API Gateway 和 CloudFront 時，Cookie 如何暴露給 Java Spark 實作。將回報的 vanity-domain 情境與現有的 serverless-java-container 文件及請求處理行為進行比較；當可以在該部署路徑中讀取 Cookie 時，即表示完成。

由索引模型根據 Issue 內容生成。