Flatten some structures.

src/wasm/additional_property.rs

@@ -9,6 +9,7 @@ use crate::types::AffiliatedKeywordValue;
 use crate::types::AffiliatedKeywords;
 
 #[derive(Debug, Serialize)]
+#[serde(untagged)]
 pub enum AdditionalPropertyValue<'s, 'p> {
     SingleString(&'s str),
     ListOfStrings(Vec<&'s str>),
@@ -21,6 +22,7 @@ pub enum AdditionalPropertyValue<'s, 'p> {
 
 #[derive(Debug, Serialize, Default)]
 pub struct AdditionalProperties<'s, 'p> {
+    #[serde(flatten)]
     pub(crate) properties: HashMap<String, AdditionalPropertyValue<'s, 'p>>,
 }