make signer wrap its public key

.gitignore

@@ -1 +1,3 @@
 /target
+
+Cargo.lock

src/signer.rs

@@ -16,6 +16,6 @@ use crate::SignatureScheme;
 pub trait Signer<K: SignatureScheme> {
     type KeyId;
     async fn sign(&self, data: &[u8]) -> Result<K::Signature>;
-    async fn public_key(&self) -> Result<K::PublicKey>;
+    fn public_key(&self) -> Result<&K::PublicKey>;
     fn key_id(&self) -> &Self::KeyId;
 }

src/storage.rs

@@ -44,8 +44,10 @@ pub trait KeyGenerate<K: SignatureScheme, I> {
 }
 
 /// KeySign trait is a trait that is used to sign a hash with a private key located in a key store. The method return a [`Signer`] object.
+#[cfg_attr(not(feature = "send-sync-storage"), async_trait(?Send))]
+#[cfg_attr(feature = "send-sync-storage", async_trait)]
 pub trait KeySign<K: SignatureScheme, I> {
-    fn get_signer(&self, key_id: &I) -> Result<impl Signer<K, KeyId = I>>;
+    async fn get_signer(&self, key_id: &I) -> Result<impl Signer<K, KeyId = I>>;
 }
 
 /// KeyDelete trait is a trait that is used to delete a key pair from the key store.