feat: auto opt-in to Business Policies and create default shipping/payment/returns policies on first post

EbayListingTool/Services/EbayListingService.cs

@@ -203,6 +203,111 @@ public class EbayListingService
         return $"Could not fetch {policyType} from eBay. Please check your account settings.";
     }
 
+    /// <summary>
+    /// Called automatically on first 20403 error. Opts the account in to SELLING_POLICY_MANAGEMENT
+    /// then creates minimal default policies so posting can proceed without manual eBay setup.
+    /// </summary>
+    private async Task SetupDefaultBusinessPoliciesAsync(string token)
+    {
+        // Step 1: opt in to the Business Policies programme
+        try
+        {
+            var optInBody = JsonConvert.SerializeObject(new { programType = "SELLING_POLICY_MANAGEMENT" });
+            using var req = MakeRequest(HttpMethod.Post,
+                $"{_auth.BaseUrl}/sell/account/v1/program/opt_in", token);
+            req.Content = new StringContent(optInBody, Encoding.UTF8, "application/json");
+            await _http.SendAsync(req); // 204 = success; ignore other responses
+        }
+        catch { /* opt-in failure is non-fatal — account may already be opted in */ }
+
+        // Step 2: create one policy of each required type (ignore errors — they may already exist)
+        await TryCreateFulfillmentPolicyAsync(token);
+        await TryCreatePaymentPolicyAsync(token);
+        await TryCreateReturnPolicyAsync(token);
+    }
+
+    private async Task TryCreateFulfillmentPolicyAsync(string token)
+    {
+        try
+        {
+            var body = new
+            {
+                name           = "Standard UK Shipping",
+                marketplaceId  = "EBAY_GB",
+                categoryTypes  = new[] { new { name = "ALL_EXCLUDING_MOTORS_VEHICLES" } },
+                handlingTime   = new { value = 1, unit = "DAY" },
+                shippingOptions = new[]
+                {
+                    new
+                    {
+                        optionType = "DOMESTIC",
+                        costType   = "FLAT_RATE",
+                        shippingServices = new[]
+                        {
+                            new
+                            {
+                                sortOrder             = 1,
+                                shippingCarrierCode   = "ROYALMAIL",
+                                shippingServiceCode   = "UK_RoyalMailSecondClass",
+                                shippingCost          = new { value = "2.85", currency = "GBP" },
+                                additionalShippingCost = new { value = "0.00", currency = "GBP" }
+                            }
+                        }
+                    }
+                }
+            };
+            using var req = MakeRequest(HttpMethod.Post,
+                $"{_auth.BaseUrl}/sell/account/v1/fulfillment_policy", token);
+            req.Content = new StringContent(
+                JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json");
+            await _http.SendAsync(req);
+        }
+        catch { }
+    }
+
+    private async Task TryCreatePaymentPolicyAsync(string token)
+    {
+        try
+        {
+            var body = new
+            {
+                name          = "Managed Payments",
+                marketplaceId = "EBAY_GB",
+                categoryTypes = new[] { new { name = "ALL_EXCLUDING_MOTORS_VEHICLES" } },
+                paymentMethods = Array.Empty<object>()
+            };
+            using var req = MakeRequest(HttpMethod.Post,
+                $"{_auth.BaseUrl}/sell/account/v1/payment_policy", token);
+            req.Content = new StringContent(
+                JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json");
+            await _http.SendAsync(req);
+        }
+        catch { }
+    }
+
+    private async Task TryCreateReturnPolicyAsync(string token)
+    {
+        try
+        {
+            var body = new
+            {
+                name                    = "Standard Returns",
+                marketplaceId           = "EBAY_GB",
+                categoryTypes           = new[] { new { name = "ALL_EXCLUDING_MOTORS_VEHICLES" } },
+                returnsAccepted         = true,
+                returnPeriod            = new { value = 30, unit = "DAY" },
+                refundMethod            = "MONEY_BACK",
+                returnShippingCostPayer = "BUYER"
+            };
+            using var req = MakeRequest(HttpMethod.Post,
+                $"{_auth.BaseUrl}/sell/account/v1/return_policy", token);
+            req.Content = new StringContent(
+                JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json");
+            await _http.SendAsync(req);
+        }
+        catch { }
+    }
+
     private async Task CreateMerchantLocationAsync(string token, string postcode)
     {
         if (string.IsNullOrWhiteSpace(postcode))