What is the hp_sum key?

[wesmattson]

On 2 different test environments I've looked at there is an hp_sum key in the deployment.yml. I do not see anything about hp_sum key in this repo. Does there need to be and hp_sum key in deployment.yml? If so, can we please add it in the example template. If the key changes or needs to be different can we add some notes on how to generate it if needed?