feat(core): flesh out CardCore + CardKind

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/idfoto-core/src/item_types/card.rs

@@ -1,7 +1,25 @@
+//! Card: number, holder, expiry (MonthYear), CVV, PIN, kind.
+
 use serde::{Deserialize, Serialize};
+use zeroize::Zeroizing;
+
+use crate::time::MonthYear;
 
 #[derive(Debug, Clone, Serialize, Deserialize, Default)]
-pub struct CardCore {}
+pub struct CardCore {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub number: Option<Zeroizing<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub holder: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub expiry: Option<MonthYear>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cvv: Option<Zeroizing<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub pin: Option<Zeroizing<String>>,
+    #[serde(default)]
+    pub kind: CardKind,
+}
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
 #[serde(rename_all = "snake_case")]
@@ -13,3 +31,38 @@ pub enum CardKind {
     Loyalty,
     Other,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn card_full_round_trip() {
+        let card = CardCore {
+            number: Some(Zeroizing::new("4111111111111111".into())),
+            holder: Some("Alice Doe".into()),
+            expiry: Some(MonthYear::new(12, 2030).unwrap()),
+            cvv: Some(Zeroizing::new("123".into())),
+            pin: Some(Zeroizing::new("0000".into())),
+            kind: CardKind::Credit,
+        };
+        let json = serde_json::to_string(&card).unwrap();
+        let parsed: CardCore = serde_json::from_str(&json).unwrap();
+        assert_eq!(parsed.holder.as_deref(), Some("Alice Doe"));
+        assert_eq!(parsed.kind, CardKind::Credit);
+        assert_eq!(parsed.expiry, Some(MonthYear::new(12, 2030).unwrap()));
+    }
+
+    #[test]
+    fn card_kind_default_is_credit() {
+        let json = "{}";
+        let card: CardCore = serde_json::from_str(json).unwrap();
+        assert_eq!(card.kind, CardKind::Credit);
+    }
+
+    #[test]
+    fn card_kind_serializes_snake_case() {
+        let json = serde_json::to_string(&CardKind::Loyalty).unwrap();
+        assert_eq!(json, "\"loyalty\"");
+    }
+}