[#472] make crypto entities and the in-memory stores impl Debug

- that allows clients of this library to avoid having to reimplement Debug for the complex in-memory
  stores if they produce their own wrappers around those stores and want to Debug those

rust/protocol/src/curve.rs

@@ -297,6 +297,16 @@ impl TryFrom<&[u8]> for PrivateKey {
     }
 }
 
+impl fmt::Debug for PrivateKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "PrivateKey {{ public_key_version={:?} }}",
+            self.public_key().expect("should always have a public key")
+        )
+    }
+}
+
 #[derive(Copy, Clone)]
 pub struct KeyPair {
     pub public_key: PublicKey,

rust/protocol/src/identity_key.rs

@@ -1,5 +1,5 @@
 //
-// Copyright 2020 Signal Messenger, LLC.
+// Copyright 2020-2022 Signal Messenger, LLC.
 // SPDX-License-Identifier: AGPL-3.0-only
 //
 
@@ -72,7 +72,7 @@ impl From<IdentityKey> for PublicKey {
     }
 }
 
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 pub struct IdentityKeyPair {
     identity_key: IdentityKey,
     private_key: PrivateKey,

rust/protocol/src/storage/inmem.rs

@@ -17,7 +17,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use uuid::Uuid;
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemIdentityKeyStore {
     key_pair: IdentityKeyPair,
     id: u32,
@@ -96,7 +96,7 @@ impl traits::IdentityKeyStore for InMemIdentityKeyStore {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemPreKeyStore {
     pre_keys: HashMap<PreKeyId, PreKeyRecord>,
 }
@@ -143,7 +143,7 @@ impl traits::PreKeyStore for InMemPreKeyStore {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemSignedPreKeyStore {
     signed_pre_keys: HashMap<SignedPreKeyId, SignedPreKeyRecord>,
 }
@@ -188,7 +188,7 @@ impl traits::SignedPreKeyStore for InMemSignedPreKeyStore {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemSessionStore {
     sessions: HashMap<ProtocolAddress, SessionRecord>,
 }
@@ -250,7 +250,7 @@ impl traits::SessionStore for InMemSessionStore {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemSenderKeyStore {
     // We use Cow keys in order to store owned values but compare to referenced ones.
     // See https://users.rust-lang.org/t/hashmap-with-tuple-keys/12711/6.
@@ -300,7 +300,7 @@ impl traits::SenderKeyStore for InMemSenderKeyStore {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct InMemSignalProtocolStore {
     pub session_store: InMemSessionStore,
     pub pre_key_store: InMemPreKeyStore,