Add hidden attribute

crates/pile-config/src/lib.rs

@@ -63,6 +63,12 @@ pub enum Source {
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct FieldSpec {
+	/// If true, do not display this field.
+	/// This attribute has no effect on pile, it
+	/// is intended for consumers of data.
+	#[serde(default)]
+	pub hidden: bool,
+
 	/// How to find this field in a data entry
 	pub path: Vec<ObjectPath>,
 }