Function macro_policy 

pub fn macro_policy(id: &str, params: &Value, trust: Trust) -> Policy

The policy for running command id with params as a macro step in a document with trust.

Any path other than null counts as touching a file: a token such as {"$ref": "Input"} becomes a path when the step runs, and exports write to "" and " " as file names. The runner checks the parameters both as written and as resolved.