docs: add list mandates for customer (#3592)

crates/openapi/src/openapi.rs

@@ -114,6 +114,7 @@ Never share your secret api keys. Keep them guarded and secure.
         routes::customers::customers_list,
         routes::customers::customers_update,
         routes::customers::customers_delete,
+        routes::customers::customers_mandates_list,
 
         //Routes for payment methods
         routes::payment_method::create_payment_method_api,

crates/openapi/src/routes/customers.rs

@@ -100,3 +100,19 @@ pub async fn customers_delete() {}
     security(("api_key" = []))
 )]
 pub async fn customers_list() {}
+
+/// Customers - Mandates List
+///
+/// Lists all the mandates for a particular customer id.
+#[utoipa::path(
+    post,
+    path = "/customers/{customer_id}/mandates",
+    responses(
+        (status = 200, description = "List of retrieved mandates for a customer", body = Vec<MandateResponse>),
+        (status = 400, description = "Invalid Data"),
+    ),
+    tag = "Customers Mandates List",
+    operation_id = "List all Mandates for a Customer",
+    security(("api_key" = []))
+)]
+pub async fn customers_mandates_list() {}