AWS Cloudformation configuration does not allow configuration of DD_LOG_LEVEL

[ohookins]

Describe what happened:
The documentation describes how to debug usage of the log forwarding lambda in AWS, by setting the DD_LOG_LEVEL environment variable, unfortunately this variable is not exposed by the Cloudformation template and so cannot be configured (at least, not without manually changing the configuration of the lambda).

Describe what you expected:
There should be a DdLogLevel template parameter to the Cloudformation template.

Steps to reproduce the issue:
Deploy the Cloudformation template and attempt to the DD_LOG_LEVEL environment variable on the lambda.