Apply suggestions from code review

keep the type_name a &'static str

Co-authored-by: Yoshua Wuyts <yoshuawuyts+github@gmail.com>

src/error.rs

@@ -15,7 +15,7 @@ pub type Result<T> = std::result::Result<T, Error>;
 pub struct Error {
     error: anyhow::Error,
     status: crate::StatusCode,
-    type_name: Option<String>,
+    type_name: Option<&'static str>,
 }
 
 impl Error {
@@ -28,7 +28,7 @@ impl Error {
         Self {
             status,
             error: error.into(),
-            type_name: Some(std::any::type_name::<E>().to_string()),
+            type_name: Some(std::any::type_name::<E>()),
         }
     }