feat: add referral qrcode generation provider

Tiku.IntegrationTests/Api/AssetManagementEndpointTests.cs

@@ -381,6 +381,23 @@ public sealed class AssetManagementEndpointTests
                 "fake-signed-url"));
         }
 
+        public Task<ObjectStorageWriteResult> WriteObjectAsync(
+            ObjectStorageWriteRequest request,
+            CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(new ObjectStorageWriteResult(
+                request.Provider,
+                request.Bucket,
+                request.ObjectKey,
+                new Uri($"https://storage.example.test/{request.ObjectKey}"),
+                request.FileSizeBytes,
+                request.MimeType,
+                request.ChecksumSha256,
+                "fake-etag",
+                new Dictionary<string, string>(),
+                "fake-write"));
+        }
+
         public Task<ObjectStorageMetadata> HeadObjectAsync(
             ObjectStorageHeadRequest request,
             CancellationToken cancellationToken = default)