"deprecate" calls to NormalizePath::default

MIGRATION.md

@@ -3,7 +3,8 @@
 * The default `NormalizePath` behavior now strips trailing slashes by default. This was
   previously documented to be the case in v3 but the behavior now matches. The effect is that
   routes defined with trailing slashes will become inaccessible when
-  using `NormalizePath::default()`.
+  using `NormalizePath::default()`. As such, calling `NormalizePath::default()` will log a warning.
+  It is advised that the `new` method be used instead.
   
   Before: `#[get("/test/")]`  
   After:  `#[get("/test")]`  

src/middleware/normalize.rs

@@ -59,7 +59,7 @@ impl Default for TrailingSlash {
 ///
 /// # actix_web::rt::System::new().block_on(async {
 /// let app = App::new()
-///     .wrap(middleware::NormalizePath::default())
+///     .wrap(middleware::NormalizePath::trim())
 ///     .route("/test", web::get().to(|| async { "test" }))
 ///     .route("/unmatchable/", web::get().to(|| async { "unmatchable" }));
 ///
@@ -85,13 +85,31 @@ impl Default for TrailingSlash {
 /// assert_eq!(res.status(), StatusCode::NOT_FOUND);
 /// # })
 /// ```
-#[derive(Debug, Clone, Copy, Default)]
+#[derive(Debug, Clone, Copy)]
 pub struct NormalizePath(TrailingSlash);
 
+impl Default for NormalizePath {
+    fn default() -> Self {
+        log::warn!(
+            "`NormalizePath::default()` is deprecated. The default trailing slash behavior changed \
+            in v4 from `Always` to `Trim`. Update your call to `NormalizePath::new(...)`."
+        );
+
+        Self(TrailingSlash::Trim)
+    }
+}
+
 impl NormalizePath {
     /// Create new `NormalizePath` middleware with the specified trailing slash style.
     pub fn new(trailing_slash_style: TrailingSlash) -> Self {
-        NormalizePath(trailing_slash_style)
+        Self(trailing_slash_style)
+    }
+
+    /// Constructs a new `NormalizePath` middleware with [trim](TrailingSlash::Trim) semantics.
+    ///
+    /// Use this instead of `NormalizePath::default()` to avoid deprecation warning.
+    pub fn trim() -> Self {
+        Self::new(TrailingSlash::Trim)
     }
 }