Use the serde_cow crate (#2814)

This replaces a manual implementation of deserialising strings into `Cow<str>`s.

Cargo.toml

@@ -30,6 +30,7 @@ dep_time = { version = "0.3.30", package = "time", features = ["formatting", "pa
 base64 = { version = "0.21.5" }
 secrecy = { version = "0.8.0", features = ["serde"] }
 arrayvec = { version = "0.7.4", features = ["serde"] }
+serde_cow = { version = "0.1.0" }
 # Optional dependencies
 fxhash = { version = "0.2.1", optional = true }
 simd-json = { version = "0.13.4", optional = true }

src/model/channel/attachment.rs

@@ -1,10 +1,11 @@
 #[cfg(feature = "model")]
 use reqwest::Client as ReqwestClient;
+use serde_cow::CowStr;
 
 #[cfg(feature = "model")]
 use crate::internal::prelude::*;
 use crate::model::prelude::*;
-use crate::model::utils::{is_false, CowStr};
+use crate::model::utils::is_false;
 
 fn base64_bytes<'de, D>(deserializer: D) -> Result<Option<Vec<u8>>, D::Error>
 where

src/model/utils.rs

@@ -1,4 +1,3 @@
-use std::borrow::Cow;
 use std::fmt;
 use std::hash::Hash;
 use std::marker::PhantomData;
@@ -83,44 +82,6 @@ where
     }
 }
 
-pub(super) struct CowStr<'de>(pub Cow<'de, str>);
-
-impl<'de> serde::Deserialize<'de> for CowStr<'de> {
-    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> StdResult<Self, D::Error> {
-        struct CowStrVisitor;
-        impl<'de> serde::de::Visitor<'de> for CowStrVisitor {
-            type Value = CowStr<'de>;
-
-            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-                formatter.write_str("a string")
-            }
-
-            fn visit_borrowed_str<E>(self, val: &'de str) -> StdResult<Self::Value, E>
-            where
-                E: serde::de::Error,
-            {
-                Ok(CowStr(Cow::Borrowed(val)))
-            }
-
-            fn visit_str<E>(self, val: &str) -> StdResult<Self::Value, E>
-            where
-                E: serde::de::Error,
-            {
-                self.visit_string(val.into())
-            }
-
-            fn visit_string<E>(self, val: String) -> StdResult<Self::Value, E>
-            where
-                E: serde::de::Error,
-            {
-                Ok(CowStr(Cow::Owned(val)))
-            }
-        }
-
-        deserializer.deserialize_string(CowStrVisitor)
-    }
-}
-
 pub(super) enum StrOrInt<'de> {
     String(String),
     Str(&'de str),
@@ -320,8 +281,7 @@ pub mod stickers {
 /// Used with `#[serde(with = "comma_separated_string")]`
 pub mod comma_separated_string {
     use serde::{Deserialize, Deserializer, Serializer};
-
-    use super::CowStr;
+    use serde_cow::CowStr;
 
     pub fn deserialize<'de, D: Deserializer<'de>>(
         deserializer: D,