Add string util for #[serde(deserialize_with = "deserialize::to_lowercase")]

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/string.rs

@@ -1,4 +1,5 @@
 mod between;
+pub mod de;
 mod split;
 mod tests;
 mod unquote;

src/core/utils/string/de.rs

@@ -0,0 +1,22 @@
+use std::fmt;
+
+use serde::de::{Deserializer, Error, Visitor};
+
+struct ToLowercase;
+
+#[inline]
+pub fn to_lowercase<'de, D>(deserializer: D) -> Result<String, D::Error>
+where
+	D: Deserializer<'de>,
+{
+	deserializer.deserialize_string(ToLowercase)
+}
+
+impl Visitor<'_> for ToLowercase {
+	type Value = String;
+
+	#[inline]
+	fn visit_str<E: Error>(self, v: &str) -> Result<Self::Value, E> { Ok(v.to_lowercase()) }
+
+	fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str("String") }
+}