refactor: update digest engine to use Result and Write, add is_supported method

src/digest_engine/none.rs

@@ -1,5 +1,7 @@
-use std::io;
+use anyhow::Result;
 use crate::digest_engine::DigestEngine;
+use std::io::{Read, Write};
+use std::io;
 
 #[derive(Debug, Eq, PartialEq, Clone, Default)]
 pub struct DigestEngineNone {}
@@ -11,14 +13,9 @@ impl DigestEngineNone {
 }
 
 impl DigestEngine for DigestEngineNone {
-    fn create(&self) -> Box<dyn DigestEngine> {
-        Box::new(Self::new())
+    fn create(&self) -> Result<Box<dyn Write>> {
+        Ok(Box::new(Self::new()))
     }
-
-    fn update(&mut self, _data: &[u8]) -> io::Result<()> {
-        Ok(())
-    }
-
     fn finalize(&mut self) -> io::Result<String> {
         Ok("none".to_string())
     }