fix(cards): Return a 200 response indicating that a customer is none (#3773)

Co-authored-by: hyperswitch-bot[bot] <148525504+hyperswitch-bot[bot]@users.noreply.github.com>

crates/api_models/src/payment_methods.rs

@@ -717,6 +717,8 @@ impl serde::Serialize for PaymentMethodList {
 pub struct CustomerPaymentMethodsListResponse {
     /// List of payment methods for customer
     pub customer_payment_methods: Vec<CustomerPaymentMethod>,
+    /// Returns whether a customer id is not tied to a payment intent (only when the request is made against a client secret)
+    pub is_guest_customer: Option<bool>,
 }
 
 #[derive(Debug, serde::Serialize, ToSchema)]

crates/router/src/core/payment_methods/cards.rs

@@ -2569,18 +2569,28 @@ pub async fn do_list_customer_pm_fetch_customer_if_not_passed(
             )
             .await?;
 
-        let customer_id = payment_intent
+        match payment_intent
             .as_ref()
             .and_then(|intent| intent.customer_id.to_owned())
-            .ok_or(errors::ApiErrorResponse::CustomerNotFound)?;
-        Box::pin(list_customer_payment_method(
-            &state,
-            merchant_account,
-            key_store,
-            payment_intent,
-            &customer_id,
-        ))
-        .await
+        {
+            Some(customer_id) => {
+                Box::pin(list_customer_payment_method(
+                    &state,
+                    merchant_account,
+                    key_store,
+                    payment_intent,
+                    &customer_id,
+                ))
+                .await
+            }
+            None => {
+                let response = api::CustomerPaymentMethodsListResponse {
+                    customer_payment_methods: Vec::new(),
+                    is_guest_customer: Some(true),
+                };
+                Ok(services::ApplicationResponse::Json(response))
+            }
+        }
     }
 }
 
@@ -2776,6 +2786,7 @@ pub async fn list_customer_payment_method(
 
     let mut response = api::CustomerPaymentMethodsListResponse {
         customer_payment_methods: customer_pms,
+        is_guest_customer: payment_intent.as_ref().map(|_| false), //to return this key only when the request is tied to a payment intent
     };
     let payment_attempt = payment_intent
         .as_ref()

openapi/openapi_spec.json

@@ -7510,6 +7510,11 @@
               "$ref": "#/components/schemas/CustomerPaymentMethod"
             },
             "description": "List of payment methods for customer"
+          },
+          "is_guest_customer": {
+            "type": "boolean",
+            "description": "Returns whether a customer id is not tied to a payment intent (only when the request is made against a client secret)",
+            "nullable": true
           }
         }
       },