fix

src/types/non_telegram_types/language_code.rs

@@ -1,6 +1,7 @@
 use serde::{Deserialize, Serialize};
 
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
 pub enum LanguageCode {
     AA,
     AB,

src/types/user.rs

@@ -40,7 +40,7 @@ mod tests {
             "first_name":"firstName",
             "last_name":"lastName",
             "username":"Username",
-            "language_code":"languageCode"
+            "language_code":"ru"
         }"#;
         let expected = User {
             id: 12345,