Using environment variables in secret_config

Heya, I’m using the “custom-token” provider for Realm authentication. As part of this configuration, I provide a number of signing keys

        "secret_config": {
            "signingKeys": [

It appears that “secret_config” is hard-coded to look up actual secrets. There doesn’t seem to be a way to add something like `%%values.custom_token_signing_key". It will instead complain that there isn’t a secret with that name.

I need to have an environment-specific signing key in order to make the key accessible to developers in a developer environment, while having a production key that isn’t available to anyone in the same way. But the nature of secret_config appears to disallow this since it must look up to a secret directly.

Is there any way around this?