Add idempotency policy validation

crates/crank-core/src/operation.rs

@@ -52,7 +52,25 @@ pub struct ResponseCachePolicy {
     pub ttl_ms: u64,
 }
 
-#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum IdempotencyMode {
+    Disabled,
+    Optional,
+    Required,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct IdempotencyPolicy {
+    pub mode: IdempotencyMode,
+    pub ttl_ms: u64,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub input_field: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub header_name: Option<String>,
+}
+
+#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
 pub struct ExecutionConfig {
     pub timeout_ms: u64,
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -60,6 +78,8 @@ pub struct ExecutionConfig {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub response_cache: Option<ResponseCachePolicy>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    pub idempotency: Option<IdempotencyPolicy>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub auth_profile_ref: Option<AuthProfileId>,
     #[serde(default, skip_serializing_if = "BTreeMap::is_empty")]
     pub headers: BTreeMap<String, String>,
@@ -352,6 +372,7 @@ updated_at: 2026-03-25T08:10:00Z
                 timeout_ms: 10_000,
                 retry_policy: None,
                 response_cache: None,
+                idempotency: None,
                 auth_profile_ref: Some(AuthProfileId::new("auth_01")),
                 headers: BTreeMap::new(),
             },