refactor(identity): follow naming conventions for conversion methods

This PR renames some method names that don't follow Rust naming conventions or behave differently from what the name suggests:
- Enforce "try" prefix on all methods that return `Result`.
- Enforce "encode" method name for methods that return encoded bytes.
- Enforce "to_bytes" method name for methods that return raw bytes.
- Enforce "decode" method name for methods that convert encoded key.
- Enforce "from_bytes" method name for methods that convert raw bytes.

Pull-Request: #3775.

identity/src/lib.rs

@@ -121,7 +121,27 @@ impl From<&PublicKey> for proto::PublicKey {
     }
 }
 
-pub use error::{DecodingError, SigningError};
+pub use error::{DecodingError, OtherVariantError, SigningError};
 pub use keypair::{Keypair, PublicKey};
 #[cfg(feature = "peerid")]
 pub use peer_id::{ParseError, PeerId};
+
+#[derive(Debug, PartialEq, Eq)]
+/// The type of key a `KeyPair` is holding.
+pub enum KeyType {
+    Ed25519,
+    RSA,
+    Secp256k1,
+    Ecdsa,
+}
+
+impl std::fmt::Display for KeyType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            KeyType::Ed25519 => f.write_str("Ed25519"),
+            KeyType::RSA => f.write_str("RSA"),
+            KeyType::Secp256k1 => f.write_str("Secp256k1"),
+            KeyType::Ecdsa => f.write_str("Ecdsa"),
+        }
+    }
+}