Provide more data from service configuration

[fredmaggiowski]

Is your feature request related to a problem? Please describe

I'd like to be able to provide more additional input data to my policies.

This feature may be used for several use cases, such as:

• provide some certificate/key for payload encryption/signing
• provide custom datasets/variables to my policies to avoid hardcoding

and more.

Describe the solution you'd like

I'd like to be able to run my policies and use the data keyword to access my contents.

e.g. Using PEM encoded certificates

allow_after_token_verified {
    mytoken := input.request.headers["My-Token"]
    pem_certificate := data.MY_PEM_CERTIFICATE
    io.jwt.verify_es256(mytoken, pem_certificate)
}

This may work with data supplied both by configuration file and environment variables.