feat: add tag to token and add support for json-schema

BREAKING CHANGE: The serialized output is no longer like
```
{"Ingredient": {"name": "foo", "amount": "1", "unit": "gr"}}
```
but instead
```
{"token": "Ingredient", "name": "foo", "amount": "1", "unit": "gr"}
```

crates/recipe-parser/Cargo.toml

@@ -12,6 +12,7 @@ homepage = { workspace = true }
 categories = ["command-line-interface", "parser-implementations"]
 
 [dependencies]
+schemars = { version = "0.8.16", optional = true }
 serde = { version = "1", features = ["derive"], optional = true }
 winnow = "0.6.6"
 
@@ -23,4 +24,9 @@ serde_json = "1.0"
 path = "src/lib.rs"
 
 [features]
+
+# Adds serde Serialize implementation to Token
 serde = ["dep:serde"]
+
+# Add JsonSchema generation for Token
+schemars = ["dep:schemars"]

crates/recipe-parser/src/parser.rs

@@ -194,6 +194,9 @@ fn parse_backstory<'a>(input: &mut Input<'a>) -> PResult<&'a str> {
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+// if you use `zod` for example, using a tag makes it easy to use an undiscriminated union
+#[cfg_attr(feature = "serde", serde(tag = "token"))]
 pub enum Token<'a> {
     Metadata {
         key: &'a str,
@@ -553,4 +556,41 @@ mod test {
         assert_eq!(expected, fmt_recipe);
         println!("{:?}", recipe);
     }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_token_serialization_works() {
+        let token = Token::Ingredient {
+            name: "quinoa",
+            quantity: Some("200"),
+            unit: Some("gr"),
+        };
+
+        let serialized = serde_json::to_string(&token).expect("failed to serialize");
+        println!("{}", serialized);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_token_serialization_creates_right_payload() {
+        let token = Token::Ingredient {
+            name: "quinoa",
+            quantity: Some("200"),
+            unit: Some("gr"),
+        };
+
+        let serialized = serde_json::to_string(&token).expect("failed to serialize");
+        assert_eq!(
+            serialized,
+            r#"{"token":"Ingredient","name":"quinoa","quantity":"200","unit":"gr"}"#
+        );
+    }
+
+    #[test]
+    #[cfg(feature = "schemars")]
+    fn test_token_json_schema_generation() {
+        use schemars::schema_for;
+        let schema = schema_for!(Token);
+        println!("{}", serde_json::to_string_pretty(&schema).unwrap());
+    }
 }