Inconsistent handling of default values for config variables in clusters-service

[foot]

Problems:

• Hard to figure out a default value of an env var sometimes
• Have to specify 10 env vars to run the cluster-service locally.

There are defaults:

• in the helm chart
• in the code if no env var value is set (if getenv("RUNTIME_NAMESPACE") == "" { ns = "default" })

Would be nice to reconcile these and have a single source of truth for default values. Which might be hard to do across both helm-charts and goland

[bigkevmcd]

We could do it with viper, or in the short-term creating a env.local file and running https://github.com/joho/godotenv#command-mode