Merge gatekeeper lists

Package Owner Merge Request

No package changes

Added Helm templating to merge lists for exceptions in OPA Gatekeeper.

The values file adds a new function that evaluates whether a customer has provided an overlay. If there is an overlap between the overlay and the default values, the default values will be concatenated onto the overlay list. And finally, the modified overlay will be used in the secret for the Helm Release on OPA Gatekeeper.

There is an undocumented flag for skipping the concatenation in case we ever need to ignore the defaults. I don't think we'll need this, but put it in as a fail safe.

Additional Details

Closes #692 (closed)