Function encode_artifact_id 

pub fn encode_artifact_id(
    app_id: &str,
    branch: &str,
    job_id: &str,
    file_name: &str,
) -> String

Encode an artifact id so GetArtifactUrl can resolve it back to its (app_id, branch, job_id, file_name) without a lookup table. AWS artifact ids are opaque; ours are a reversible base64url blob.