Allow extra env

[Turgon37]

Hello,

I need extra env to allow a parent chart to pass

unpoller:
  extraEnv:
  - name: UP_UNIFI_CONTROLLER_0_URL
    value: "https://unifiunpoller:8443"
  - name: UP_UNIFI_CONTROLLER_0_USER
    valueFrom:
      secretKeyRef:
        name: unifi-metrics-credentials
        key: username
  - name: UP_UNIFI_CONTROLLER_0_PASS
    valueFrom:
      secretKeyRef:
        name: unifi-metrics-credentials
        key: password

without needed to edit the configmap containing the "complex" file