ctap2-proto: Add raw module with RawSubcommand to authenticator::credential::management

RawSubcommand is de/serialized as a u8 corresponding to its subCommand
number.

Also implements Display for authenticator::credential::management::Error
so that it can be used as the serde error type for RawSubcommand.

crates/ctap2-proto/src/authenticator/credential/management.rs

@@ -3,6 +3,9 @@ use fido_common::credential::public_key;
 
 pub type PinUvAuthParam = [u8; 16];
 
+#[cfg(feature = "serde")]
+mod raw;
+
 #[derive(Clone, Copy)]
 pub enum Request<'a> {
     GetCredentialsMetadata {
@@ -106,3 +109,17 @@ pub enum Error {
     NoCredentials,
     KeyStoreFull,
 }
+
+impl Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let message = match self {
+            Error::PinUvAuthTokenRequired => "PIN/UV auth token required",
+            Error::MissingParameter => "Missing parameter",
+            Error::InvalidParameter => "Invalid parameter",
+            Error::PinAuthInvalid => "PIN auth invalid",
+            Error::NoCredentials => "No credentials",
+            Error::KeyStoreFull => "Key store full",
+        };
+        write!(f, "{}", message)
+    }
+}

crates/ctap2-proto/src/authenticator/credential/management/raw.rs

@@ -0,0 +1,37 @@
+use super::Error;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
+#[serde(into = "u8", try_from = "u8")]
+enum RawSubcommand {
+    GetCredsMetadata = 0x01,
+    EnumerateRpsBegin = 0x02,
+    EnumerateRpsGetNextRp = 0x03,
+    EnumerateCredentialsBegin = 0x04,
+    EnumerateCredentialsGetNextCredential = 0x05,
+    DeleteCredential = 0x06,
+    UpdateUserInformation = 0x07,
+}
+
+impl From<RawSubcommand> for u8 {
+    fn from(val: RawSubcommand) -> Self {
+        val as u8
+    }
+}
+
+impl TryFrom<u8> for RawSubcommand {
+    type Error = Error;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        Ok(match value {
+            0x01 => RawSubcommand::GetCredsMetadata,
+            0x02 => RawSubcommand::EnumerateRpsBegin,
+            0x03 => RawSubcommand::EnumerateRpsGetNextRp,
+            0x04 => RawSubcommand::EnumerateCredentialsBegin,
+            0x05 => RawSubcommand::EnumerateCredentialsGetNextCredential,
+            0x06 => RawSubcommand::DeleteCredential,
+            0x07 => RawSubcommand::UpdateUserInformation,
+            _ => return Err(Error::InvalidParameter),
+        })
+    }
+}