feat: Update the Read me and version bump for Major Release

CHANGELOG.md

@@ -1,5 +1,23 @@
 # Changelog
 
+## [v1.0.0](https://github.com/contentstack/contentstack-management-dotnet/tree/v1.0.0)(2026-07-13)
+
+ - **Breaking Change**
+   - `Newtonsoft.Json` is no longer a dependency — all JSON serialisation now uses `System.Text.Json`
+   - `client.SerializerSettings` (`JsonSerializerSettings`) replaced by `client.SerializerOptions` (`JsonSerializerOptions`)
+   - `response.OpenJObjectResponse()` removed — use `response.OpenJsonObjectResponse()` (`JsonObject`) or `response.OpenTResponse<T>()` instead
+   - `JObjectParameterValue` now accepts `System.Text.Json.Nodes.JsonNode` instead of `Newtonsoft.Json.Linq.JObject`
+   - All `[JsonProperty]` attributes replaced with `[JsonPropertyName]`
+   - Requires **.NET 10** or later
+ - **New**
+   - **Branch management**: `Branch` model with `Create`, `CreateAsync`, `Fetch`, `FetchAsync`, `Delete`, `DeleteAsync`, and `Query` operations via `Stack.Branch(uid?)`
+   - **Multi-region endpoint resolution** via `Endpoint.GetContentstackEndpoint(region, service)` — 7 regions (NA, EU, AU, Azure-NA, Azure-EU, GCP-NA, GCP-EU) and 18 service keys
+   - **OAuth auto token refresh** wired into the request pipeline
+   - **PreviewToken** support — `Create` and `Delete` operations
+   - **Image format upload**: JPEG, AVIF, and multi-format asset upload coverage
+ - **Migration Guide**
+   - See [Migrating from Newtonsoft.Json to System.Text.Json](https://www.contentstack.com/docs/developers/sdks/content-management-sdk/dot-net/migrate-dotnet-management-sdk-from-newtonsoft.json-to-system.text.json) for the full upgrade path from v0.x.
+
 ## [v1.0.0-beta.2](https://github.com/contentstack/contentstack-management-dotnet/tree/v1.0.0-beta.2)(2026-06-22)
 
  - **Chore**
@@ -157,4 +175,4 @@
 
 ## [v0.1.1](https://github.com/contentstack/contentstack-management-dotnet/tree/v0.1.1) (2022-12-16)
 
-## [v0.1.0](https://github.com/contentstack/contentstack-management-dotnet/tree/v0.1.0) (2022-10-19)
+## [v0.1.0](https://github.com/contentstack/contentstack-management-dotnet/tree/v0.1.0) (2022-10-19)

Directory.Build.props

@@ -1,5 +1,5 @@
 <Project>
   <PropertyGroup>
-    <Version>1.0.0-beta.2</Version>
+    <Version>1.0.0</Version>
   </PropertyGroup>
 </Project>

README.md

@@ -10,7 +10,9 @@ Note: By using CMA, you can execute GET requests for fetching content. However,
 
 ### Prerequisite
 
-You need .NET installed on your machine to use the Contentstack .NET CMA SDK.
+You need .NET 10 or above installed on your machine to use the Contentstack .NET CMA SDK.
+
+> **Migrating from v0.x?** Version 1.0.0 replaces Newtonsoft.Json with System.Text.Json and changes several public API signatures (e.g. `OpenJObjectResponse()` → `OpenJsonObjectResponse()`, `SerializerSettings` → `SerializerOptions`). See the [migration guide](https://www.contentstack.com/docs/developers/sdks/content-management-sdk/dot-net/migrate-dotnet-management-sdk-from-newtonsoft.json-to-system.text.json) before upgrading.
 
 ### Installation
 Open the terminal and install the contentstack module via ‘Package Manager’ command
@@ -99,12 +101,80 @@ contentstackConfig.ProxyPort = 9000;
 contentstackConfig.ProxyCredentials = new NetworkCredential(userName: "username", password: "password");
 ContentstackClient client = new ContentstackClient(new OptionsWrapper<ContentstackClientOptions>(options));
 ```
+#### OAuth Authentication
+As an alternative to Authtoken/Management Token authentication, you can use OAuth 2.0:
+```c#
+ContentstackClient client = new ContentstackClient();
+var oauthOptions = new OAuthOptions
+{
+    AppId = "your-app-id",
+    ClientId = "your-client-id",
+    RedirectUri = "http://localhost:8184"
+};
+OAuthHandler oauthHandler = client.OAuth(oauthOptions);
+
+// Get authorization URL
+string authUrl = oauthHandler.GetAuthorizationUrl();
+
+// After user authorization, exchange code for tokens
+var tokens = await oauthHandler.ExchangeCodeForTokenAsync("authorization_code");
+```
+> Note: Once authenticated, the SDK automatically refreshes expired OAuth tokens before making API calls — no manual token refresh required.
+
+#### Branch Management
+Use the `Branch` model to create, fetch, delete, and query branches for a stack:
+```c#
+ContentstackClient client = new ContentstackClient("<AUTHTOKEN>", "<API_HOST>");
+
+// Create a branch
+BranchModel model = new BranchModel() { Uid = "my-branch", Source = "main" };
+ContentstackResponse createResponse = client.Stack("<API_KEY>").Branch().Create(model);
+
+// Fetch a branch
+ContentstackResponse fetchResponse = client.Stack("<API_KEY>").Branch("my-branch").Fetch();
+
+// Query all branches
+ContentstackResponse queryResponse = client.Stack("<API_KEY>").Branch().Query().Find();
+
+// Delete a branch
+ContentstackResponse deleteResponse = client.Stack("<API_KEY>").Branch("my-branch").Delete();
+```
+
+#### Preview Token
+Use `PreviewToken` to create or delete a Preview Token for a Delivery Token (compatible only with the `rest-preview.contentstack.com` endpoint):
+```c#
+ContentstackClient client = new ContentstackClient("<AUTHTOKEN>", "<API_HOST>");
+
+// Create a preview token
+PreviewTokenModel model = new PreviewTokenModel() { Name = "My Preview Token" };
+ContentstackResponse createResponse = client.Stack("<API_KEY>").PreviewToken("<DELIVERY_TOKEN_UID>").Create(model);
+
+// Delete a preview token
+ContentstackResponse deleteResponse = client.Stack("<API_KEY>").PreviewToken("<DELIVERY_TOKEN_UID>").Delete();
+```
+
+#### Multi-region Endpoint Resolution
+Use the `Endpoint` class to resolve Contentstack service URLs for any supported region without hardcoding hosts:
+```c#
+using Contentstack.Management.Core.Endpoints; // Endpoint
+
+// Resolve the Content Management endpoint for a region
+string url = Endpoint.GetContentstackEndpoint("us", "contentManagement");
+
+// Strip the https:// scheme — useful when passing the host directly to SDK configuration
+var options = new ContentstackClientOptions
+{
+    Host = Endpoint.GetContentstackEndpoint("eu", "contentManagement", omitHttps: true)
+};
+```
+
 #### Fetch Stack Detail
 Use the following lines of code to fetch your stack detail using this SDK:
 ```c#
 ContentstackResponse contentstackResponse = client.Stack("<API_KEY>").Fetch();
 
-var response = contentstackResponse.OpenJObjectResponse();
+var response = contentstackResponse.OpenJsonObjectResponse();
+string title = response["title"]?.GetValue<string>();
 // or
 StackResponse model = contentstackResponse.OpenTResponse<StackResponse>();
 ```