feat: add write conflict resolution options

CHANGELOG.md

@@ -7,19 +7,26 @@
   - per-request headers support via `Headers` property on all client options classes
   - `IRequestOptions` interface and `RequestOptions` class for API-level header support
   - `IClientRequestOptions` interface and `ClientRequestOptions` class for client-level header support
-  - add header validation to prevent overiding of reserved headers
+  - add header validation to prevent overriding of reserved headers
+- feat: add write conflict resolution options
+  - `ConflictOptions` to control behavior for duplicate writes and missing deletes
+  - `OnDuplicateWrites` option: `Error` (default) or `Ignore` for handling duplicate tuple writes
+  - `OnMissingDeletes` option: `Error` (default) or `Ignore` for handling missing tuple deletes
+  - Available in `ClientWriteOptions.Conflict` property
 
 [!WARNING]
 BREAKING CHANGES:
 
 - **OpenFgaApi methods**: All API methods now accept an `IRequestOptions? options` parameter. If you are using the low-level `OpenFgaApi` directly, you may need to update your calls:
 
   Before:
+
   ```csharp
   await api.Check(storeId, body, cancellationToken);
   ```
 
   After:
+
   ```csharp
   var options = new RequestOptions {
       Headers = new Dictionary<string, string> { { "X-Custom-Header", "value" } }
@@ -30,11 +37,13 @@ BREAKING CHANGES:
 - **ClientRequestOptions renamed**: The base client request options interface has been renamed from `ClientRequestOptions` to `IClientRequestOptions` to better follow .NET naming conventions. A concrete `ClientRequestOptions` class is now also available. If you were casting to or implementing this interface, update your code:
 
   Before:
+
   ```csharp
   var options = obj as ClientRequestOptions;
   ```
 
   After:
+
   ```csharp
   var options = obj as IClientRequestOptions;
   ```

README.md

@@ -574,6 +574,45 @@ var options = new ClientWriteOptions {
 var response = await fgaClient.Write(body, options);
 ```
 
+##### Conflict Options for Write Operations
+
+The SDK allows you to control how write conflicts are handled using the `Conflict` option:
+
+- **OnDuplicateWrites**: Controls behavior when writing a tuple that already exists
+  - `OnDuplicateWrites.Error` - Return error on duplicates (default)
+  - `OnDuplicateWrites.Ignore` - Silently skip duplicate writes
+
+- **OnMissingDeletes**: Controls behavior when deleting a tuple that doesn't exist
+  - `OnMissingDeletes.Error` - Return error on missing deletes (default)
+  - `OnMissingDeletes.Ignore` - Silently skip missing deletes
+
+```csharp
+var body = new ClientWriteRequest() {
+    Writes = new List<ClientTupleKey> {
+        new() {
+            User = "user:81684243-9356-4421-8fbf-a4f8d36aa31b",
+            Relation = "viewer",
+            Object = "document:0192ab2a-d83f-756d-9397-c5ed9f3cb69a",
+        }
+    },
+    Deletes = new List<ClientTupleKeyWithoutCondition> {
+        new() {
+            User = "user:81684243-9356-4421-8fbf-a4f8d36aa31b",
+            Relation = "writer",
+            Object = "document:0192ab2a-d83f-756d-9397-c5ed9f3cb69a",
+        }
+    },
+};
+var options = new ClientWriteOptions {
+    AuthorizationModelId = "01GXSA8YR785C4FYS3C0RTG7B1",
+    Conflict = new ConflictOptions {
+        OnDuplicateWrites = OnDuplicateWrites.Ignore,
+        OnMissingDeletes = OnMissingDeletes.Ignore
+    }
+};
+var response = await fgaClient.Write(body, options);
+```
+
 #### Relationship Queries
 
 ##### Check