feat: set env from user managed secrets/configmaps

[keyurbhole]

Summary:
This PR allows the user to have flexibility defining environment variables. via langfuse.additionalEnv. It ensures the env value can be assigned by any means for eg.

env:
  - name: LANGFUSE_LOG_LEVEL
    value: info
  - name: DATABASE_PASSWORD
    valueFrom:
      secretKeyRef:
        key: langfuse-database-password
        name: my-secrets
  - name: EMAIL_FROM_ADDRESS
    valueFrom:
      configMapKeyRef:
        key: email-from-addres
        name: my-configmap

I have also added examples/values-example.yaml file for reference.

I know there are open PR,

1. Add Database ValueFrom #14 : It has used valueFrom, but only for env variables mentioned in values.yaml file and it does not address other variables mentioned in docs like S3 keys/secrets, smtp connection url, etc.
2. feat: support nested maps in langfuse.additionalEnv #18 : It kind of solves but I think there is indentation issue

[CLAassistant]

All committers have signed the CLA.

[Steffen911]

Great addition! Thank you very much for your contribution @keyurbhole.