fix props deserialization (quick-xml doesn't support untagged enums)

crates/carddav/src/principal/mod.rs

@@ -38,11 +38,11 @@ pub enum PrincipalProp {
     #[serde(rename = "CARD:principal-address")]
     PrincipalAddress(Option<HrefElement>),
 
-    #[serde(skip_deserializing, untagged)]
+    #[serde(skip_deserializing, rename = "$value")]
     #[from]
     ExtCommonProperties(CommonPropertiesProp),
 
-    #[serde(untagged)]
+    #[serde(other)]
     #[default]
     Invalid,
 }