Purge queue table will fill up over time on non-prod environments

Problem/Motivation

Since 🐛 Missing purger error when module is enabled locally Active the purger is enabled on all environments. On local environments the invalidations silently succeed based on the DEV_MODE environment variable, however on non-prod govcms environments the purge_queue table will gradually grow over time as more and more invalidations fail if the AKAMAI environment variables don't exist.

Steps to reproduce

Deploy to environments without AKAMAI_* environment variables set.

Proposed resolution

Check for LAGOON_ENVIRONMENT_TYPE as well. AFAIK the Akamai Purge Service is production only.