Add Result alias (#271)

Adds a `yubikey::Result` alias with `yubikey::Error` as the error type.

Since we only have one `Error` type, this simplifies the return types
where a `Result` is returned.

src/metadata.rs

@@ -33,7 +33,7 @@
 use std::marker::PhantomData;
 use zeroize::Zeroizing;
 
-use crate::{error::Error, serialization::*, transaction::Transaction, Buffer};
+use crate::{serialization::*, transaction::Transaction, Buffer, Error, Result};
 
 #[cfg(feature = "untested")]
 use crate::{CB_OBJ_MAX, CB_OBJ_TAG_MAX};
@@ -78,7 +78,7 @@ impl<T: MetadataType> Default for Metadata<T> {
 
 impl<T: MetadataType> Metadata<T> {
     /// Read metadata
-    pub(crate) fn read(txn: &Transaction<'_>) -> Result<Self, Error> {
+    pub(crate) fn read(txn: &Transaction<'_>) -> Result<Self> {
         let data = txn.fetch_object(T::obj_id())?;
         Ok(Metadata {
             inner: Tlv::parse_single(data, T::tag())?,
@@ -88,7 +88,7 @@ impl<T: MetadataType> Metadata<T> {
 
     /// Write metadata
     #[cfg(feature = "untested")]
-    pub(crate) fn write(&self, txn: &Transaction<'_>) -> Result<(), Error> {
+    pub(crate) fn write(&self, txn: &Transaction<'_>) -> Result<()> {
         if self.inner.len() > CB_OBJ_MAX - CB_OBJ_TAG_MAX {
             return Err(Error::GenericError);
         }
@@ -105,12 +105,12 @@ impl<T: MetadataType> Metadata<T> {
 
     /// Delete metadata
     #[cfg(feature = "untested")]
-    pub(crate) fn delete(txn: &Transaction<'_>) -> Result<(), Error> {
+    pub(crate) fn delete(txn: &Transaction<'_>) -> Result<()> {
         txn.save_object(T::obj_id(), &[])
     }
 
     /// Get metadata item
-    pub(crate) fn get_item(&self, tag: u8) -> Result<&[u8], Error> {
+    pub(crate) fn get_item(&self, tag: u8) -> Result<&[u8]> {
         let mut data = &self.inner[..];
 
         while !data.is_empty() {
@@ -128,7 +128,7 @@ impl<T: MetadataType> Metadata<T> {
 
     /// Set metadata item
     #[cfg(feature = "untested")]
-    pub(crate) fn set_item(&mut self, tag: u8, item: &[u8]) -> Result<(), Error> {
+    pub(crate) fn set_item(&mut self, tag: u8, item: &[u8]) -> Result<()> {
         let mut cb_temp: usize = 0;
         let mut tag_temp: u8 = 0;
         let mut cb_len: usize = 0;