Add Error::method to set a custom error message

This enables updating the message without creating a binding.

Cargo.toml

@@ -3,7 +3,7 @@ name = "tower-lsp"
 version = "0.20.0"
 authors = ["Eyal Kalderon <[email protected]>"]
 edition = "2021"
-rust-version = "1.65.0"
+rust-version = "1.64.0"
 description = "Language Server Protocol implementation based on Tower"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/ebkalderon/tower-lsp"

rust-toolchain

@@ -1 +1 @@
-1.65.0
+1.64.0

src/jsonrpc/error.rs

@@ -171,6 +171,15 @@ impl Error {
     pub const fn content_modified() -> Self {
         Error::new(ErrorCode::ContentModified)
     }
+
+    /// Sets a custom `message`.
+    pub fn message<M>(mut self, message: M) -> Self
+    where
+        M: Into<Cow<'static, str>>,
+    {
+        self.message = message.into();
+        self
+    }
 }
 
 impl Display for Error {