feature(proposal): Bindings for system environment variable

[pmbanugo]

At the moment I have to put the values for environment variables as key bindings. I'd like a way to read system environment variables similar to process.env in Node.js. Perhaps one way to make it work could be explicitly binding to a system environment variable. Another option could be specifying it via the runtime/cli.

[kentonv]

I think it would make sense to allow a text binding to take its value from an environment variable, and this should be easy to implement.

So like:

binding = (name = "bindingName", (fromEnvironment = "VAR_NAME"))

It's important that this be declared explicitly, though, so that secrets from the environment don't accidentally leak to workers.

[josephpage]

This would be an excellent evolution, since today there is no way to give a variable or a secret to a worker without putting it in clear text in the capnp file. The interface proposed by @kentonv would suit very well.

[kentonv]

Implemented in #786. Sorry it took a while, been backlogged.