radicle-crypto: add Serialize and Deserialize for Signature

Add Serialize and Deserialize for Signature using the the `into` and
`try_from` serde attributes. To achieve this `From` and `TryFrom`
implementations were added between `Signature` and `String`.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle-crypto/src/lib.rs

@@ -63,7 +63,8 @@ where
 }
 
 /// Cryptographic signature.
-#[derive(PartialEq, Eq, Copy, Clone)]
+#[derive(PartialEq, Eq, Copy, Clone, Serialize, Deserialize)]
+#[serde(into = "String", try_from = "String")]
 pub struct Signature(pub ed25519::Signature);
 
 impl fmt::Display for Signature {
@@ -126,6 +127,20 @@ impl TryFrom<&[u8]> for Signature {
     }
 }
 
+impl From<Signature> for String {
+    fn from(s: Signature) -> Self {
+        s.to_string()
+    }
+}
+
+impl TryFrom<String> for Signature {
+    type Error = SignatureError;
+
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        Self::from_str(&s)
+    }
+}
+
 /// The public/verification key.
 #[derive(Serialize, Deserialize, Eq, Copy, Clone)]
 #[serde(into = "String", try_from = "String")]