[ISSUE #1489]📝Update rocketmq-macros README.md (#1490)

rocketmq-macros/README.md

@@ -1,5 +1,44 @@
-# The Rust Implementation of Apache RocketMQ macros
+# RocketMQ-Rust Macros
+
+Using macros to automate repetitive tasks.
 
 ## Overview
 
-The entire set of common macros for RocketMQ-Rust is implemented in this module.
+This crate is primarily for the macros used in RocketMQ-Rust. The currently defined macros are as follows:
+
+- **RequestHeaderCodec([Derive Macros](https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros))**
+- **RemotingSerializable([Derive Macros](https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros))** - Currently not in use, implemented via alternative methods.
+
+## RequestHeaderCodec Macro
+
+The `RequestHeaderCodec` macro implements serialization and deserialization for RocketMQ's `RequestHeader`. It automatically implements the **`CommandCustomHeader trait`** and the **`FromMap trait`**. This macro includes an attribute: **`required`**, which indicates that a field of the struct must be present during deserialization; otherwise, it will result in an error.
+
+> Note: The `required` attribute corresponds to the `@CFNotNull` annotation in the Java version and is implemented in this way in Rust.
+
+Example usage is shown below:
+
+```rust
+#[derive(Debug, Clone, Serialize, Deserialize, Default, RequestHeaderCodec)]
+#[serde(rename_all = "camelCase")]
+pub struct SendMessageRequestHeader {
+    #[required]  // this field is required
+    pub producer_group: CheetahString,
+    pub topic: CheetahString,
+    pub default_topic: CheetahString,
+    pub default_topic_queue_nums: i32,
+    pub queue_id: Option<i32>,
+    pub sys_flag: i32,
+    pub born_timestamp: i64,
+    pub flag: i32,
+    pub properties: Option<CheetahString>,
+    pub reconsume_times: Option<i32>,
+    pub unit_mode: Option<bool>,
+    pub batch: Option<bool>,
+    pub max_reconsume_times: Option<i32>,
+    #[serde(flatten)]
+    pub topic_request_header: Option<TopicRequestHeader>,
+}
+```
+
+In this example, the `SendMessageRequestHeader` struct is annotated with the `RequestHeaderCodec` derive macro, along with other standard Rust attributes like `Debug`, `Clone`, `Serialize`, `Deserialize`, and `Default`. The `#[required]` attribute is used on the `producer_group` field to denote that it is mandatory for successful deserialization.
+