stack/kustomizations/nextcloud/env-vars-patch.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
spec:
  template:
    spec:
      containers:
        - name: app
          env:
            - name: PG_HOST
              value: $(DB_SERVICE)
            - name: REDIS_HOST
              value: $(REDIS_SERVICE)