misc: replace manual From<T> for *Error with #[from]

This is a small simplification we can use since we use `thiserror`
anyway. Note that `#[from]` implies `#[source]` [0].

[0]: https://docs.rs/thiserror/2.0.12/thiserror/index.html

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

vmm/src/api/http/mod.rs

@@ -44,7 +44,7 @@ pub type HttpApiHandle = (thread::JoinHandle<Result<()>>, EventFd);
 pub enum HttpError {
     /// API request receive error
     #[error("Failed to deserialize JSON: {0}")]
-    SerdeJsonDeserialize(#[source] SerdeError),
+    SerdeJsonDeserialize(#[from] SerdeError),
 
     /// Attempt to access unsupported HTTP method
     #[error("Bad Request")]
@@ -67,12 +67,6 @@ pub enum HttpError {
     ApiError(#[source] ApiError),
 }
 
-impl From<serde_json::Error> for HttpError {
-    fn from(e: serde_json::Error) -> Self {
-        HttpError::SerdeJsonDeserialize(e)
-    }
-}
-
 const HTTP_ROOT: &str = "/api/v1";
 
 pub fn error_response(error: HttpError, status: StatusCode) -> Response {