Add docs for CustomHeadersBuilder option of NATS. (#1519)

docs/content/user-guide/en/transport/nats.md

@@ -45,6 +45,7 @@ ConnectionPoolSize  | number of connections pool | uint | 10
 DeliverPolicy | The point in the stream to receive messages from (⚠️ Removed from version 8.1.0, use `ConsumerOptions` instead.) | enum | DeliverPolicy.New
 StreamOptions | 🆕 Stream configuration |  Action | NULL
 ConsumerOptions | 🆕 Consumer configuration | Action | NULL
+CustomHeadersBuilder | Custom subscribe headers |  See the blow | NULL
 
 #### NATS ConfigurationOptions
 
@@ -62,3 +63,22 @@ services.AddCap(capOptions =>
 ```
 
 `Options` is a NATS.Client ConfigurationOptions , you can find more details through this [link](http://nats-io.github.io/nats.net/class_n_a_t_s_1_1_client_1_1_options.html)
+
+#### CustomHeadersBuilder Option
+
+When the message sent from a heterogeneous system, because of the CAP needs to define additional headers, so an exception will occur at this time. By providing this parameter to set the custom headersn to make the subscriber works.
+
+You can find the description of [Header Information](../cap/messaging.md#heterogeneous-system-integration) here.
+
+Example：
+
+```cs
+x.UseNATS(aa =>
+{
+    aa.CustomHeadersBuilder = (e, sp) =>
+    [
+        new(DotNetCore.CAP.Messages.Headers.MessageId, sp.GetRequiredService<ISnowflakeId>().NextId().ToString()),
+        new(DotNetCore.CAP.Messages.Headers.MessageName, e.Message.Subject)
+    ];
+});
+```

docs/content/user-guide/zh/transport/nats.md

@@ -46,6 +46,7 @@ ConnectionPoolSize  | 连接池数量 | uint | 10
 DeliverPolicy | 消费消息的策略点（⚠️在8.1.0版本移除，使用`ConsumerOptions`替代。） | enum | DeliverPolicy.New
 StreamOptions | 🆕 Stream 配置项 |  Action | NULL
 ConsumerOptions | 🆕 Consumer 配置项 | Action | NULL
+CustomHeadersBuilder | 订阅者自定义头信息 |  见下文 |  N/A
 
 #### NATS ConfigurationOptions
 
@@ -63,3 +64,22 @@ services.AddCap(capOptions =>
 ```
 
 `Options` 是 NATS.Client 客户端提供的配置， 你可以在这个[链接](http://nats-io.github.io/nats.net/class_n_a_t_s_1_1_client_1_1_options.html)找到更多详细信息。
+
+#### CustomHeadersBuilder Option
+
+当需要从异构系统或者直接接收从 NATS JetStream 发送的消息时，由于 CAP 需要定义额外的头信息才能正常订阅，所以此时会出现异常。通过提供此参数来进行自定义头信息的设置来使订阅者正常工作。
+
+你可以在这里找到有关 [头信息](../cap/messaging.md#异构系统集成) 的说明。
+
+用法如下：
+
+```cs
+x.UseNATS(aa =>
+{
+    aa.CustomHeadersBuilder = (e, sp) =>
+    [
+        new(DotNetCore.CAP.Messages.Headers.MessageId, sp.GetRequiredService<ISnowflakeId>().NextId().ToString()),
+        new(DotNetCore.CAP.Messages.Headers.MessageName, e.Message.Subject)
+    ];
+});
+```