feat(documentation): add polymorphic generate_schema macro (#1183)

Co-authored-by: pixincreate@work <69745008+pixincreate@users.noreply.github.com>

crates/api_models/src/refunds.rs

@@ -45,6 +45,7 @@ pub struct RefundRequest {
     pub metadata: Option<pii::SecretSerdeValue>,
 
     /// Merchant connector details used to make payments.
+    #[schema(value_type = Option<MerchantConnectorDetailsWrap>)]
     pub merchant_connector_details: Option<admin::MerchantConnectorDetailsWrap>,
 }