CI: fix rust-nightly static checks

Signed-off-by: Chris Porter <[email protected]>

image-rs/src/resource/mod.rs

@@ -30,6 +30,7 @@ lazy_static::lazy_static! {
 /// - `SCHEME`: `file` string, to distinguish different uri scheme
 /// - `get_resource()`: get resource from the uri
 #[async_trait]
+#[allow(dead_code)]
 trait Protocol: Send + Sync {
     async fn get_resource(&mut self, uri: &str) -> Result<Vec<u8>>;
 }

image-rs/src/signature/image/digest.rs

@@ -76,9 +76,9 @@ impl Digest {
     }
 }
 
-impl ToString for Digest {
-    fn to_string(&self) -> String {
-        format!("{}:{}", self.algorithm, self.value)
+impl fmt::Display for Digest {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}:{}", self.algorithm, self.value)
     }
 }