improve serde representation

Author: GyulyVGC

src/enums/operator.rs

@@ -1,6 +1,7 @@
 use serde::{Deserialize, Serialize};
 
 #[derive(PartialEq, Copy, Clone, Debug, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
 pub enum Operator {
     And,
     Or,

src/enums/postfix_token.rs

@@ -2,6 +2,7 @@ use serde::{Deserialize, Serialize};
 use crate::enums::operator::Operator;
 
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case", tag = "type")]
 pub enum PostfixToken<Predicate> {
     Operator(Operator),
     Predicate(Predicate),