feat: Adding deprecation fields to InputValue (#553)

* feat: Adding deprecation fields to InpuValue

This  will support deprecated directive on  InputValue as defined in https://spec.graphql.org/September2025/#sec--deprecated

* feat: Adding serde default to new fields

New fields should have default serde values in order to keep backward compatibility.

Author: lpessoa

graphql-introspection-query/src/introspection_response.rs

@@ -202,6 +202,10 @@ pub struct InputValue {
     #[serde(rename = "type")]
     pub type_: InputValueType,
     pub default_value: Option<String>,
+    #[serde(default)]
+    pub is_deprecated: Option<bool>,
+    #[serde(default)]
+    pub deprecation_reason: Option<String>,
 }
 
 type InputValueType = TypeRef;