Derive Macro SensitiveError 

#[derive(SensitiveError)]
{
    // Attributes available to this derive:
    #[sensitive]
    #[error]
}

Derives redaction::SensitiveType for types that should log without Serialize.

This emits the same traversal and redacted Debug impls as Sensitive, but uses a slog::Value implementation that logs a redacted string derived from a display template.

The display template is taken from #[error("...")] (thiserror-style) or from doc comments (displaydoc-style). If neither is present, the derive fails with a compile error to avoid accidental exposure of sensitive fields.

The generated Display implementation suppresses unused_variables/unused_assignments warnings in its match arm bindings, since omission from the template is often intentional.

Classified fields referenced in the template are redacted by applying the policy to an owned copy of the field value, so those field types must implement Clone.