feat(refunds): add connector field in refund response (#1059)

Co-authored-by: Sarthak Soni <76486416+Sarthak1799@users.noreply.github.com>

crates/api_models/src/refunds.rs

@@ -120,6 +120,9 @@ pub struct RefundResponse {
     /// The timestamp at which refund is updated
     #[serde(with = "common_utils::custom_serde::iso8601::option")]
     pub updated_at: Option<PrimitiveDateTime>,
+    /// The connector used for the refund and the corresponding payment
+    #[schema(example = "stripe")]
+    pub connector: String,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Deserialize, Serialize, ToSchema)]