Add Display formatter to SlotId (#353)

src/piv.rs

@@ -57,6 +57,7 @@ use log::{debug, error, warn};
 use p256::NistP256;
 use p384::NistP384;
 use rsa::{BigUint, RsaPublicKey};
+use std::fmt::{Display, Formatter};
 use std::str::FromStr;
 
 #[cfg(feature = "untested")]
@@ -153,6 +154,15 @@ impl From<SlotId> for u8 {
     }
 }
 
+impl Display for SlotId {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            SlotId::Retired(r) => write!(f, "{:?}", r),
+            _ => write!(f, "{:?}", self),
+        }
+    }
+}
+
 impl FromStr for SlotId {
     type Err = Error;
 
@@ -295,6 +305,12 @@ impl From<RetiredSlotId> for u8 {
     }
 }
 
+impl Display for RetiredSlotId {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
 impl RetiredSlotId {
     /// Returns the [`ObjectId`] that corresponds to a given [`RetiredSlotId`].
     pub(crate) fn object_id(self) -> ObjectId {