XnLemon opened a new pull request, #3619:
URL: https://github.com/apache/dubbo-go/pull/3619
### Description
#3598 - Task 17
Improve the documentation for `ServiceInfo` metadata conversion:
- Explain how `NewServiceInfoWithURL` projects an exported provider URL into
service-level metadata.
- Document parameter filtering and the compact representation of
method-level parameters.
- Clarify how `GetMethods` decodes the serialized method list.
- Explain how `GetParams` restores method parameters for consumer URL
reconstruction.
- Document that the original URL is retained only as a local runtime
reference and is excluded from serialization.
This change only improves code comments and does not alter runtime behavior.
---
Why
<details>
<summary>中文说明</summary>
### 变更说明
完善 `ServiceInfo` 元数据转换相关注释：
- 说明 `NewServiceInfoWithURL` 如何将 Provider URL 转换为服务级元数据。
- 解释服务参数筛选和方法级参数的紧凑存储格式。
- 说明 `GetMethods` 如何恢复方法列表。
- 说明 `GetParams` 如何还原消费者 URL 所需的方法参数。
- 明确原始 URL 仅作为本地运行时引用，不参与序列化。
本次变更仅补充代码注释，不改变运行时行为。
---
### 回答: 为什么 URL 需要被抽取？
这里抽取的是 MetadataService URL 的参数，不是普通业务服务 URL。
核心原因是解决一个“启动信息从哪里来”的问题：
```text
消费者需要 MetadataInfo，才能知道应用提供哪些业务服务
消费者需要调用 MetadataService，才能拿到 MetadataInfo
消费者需要 MetadataService URL，才能调用 MetadataService
```
因此不能把 MetadataService URL 只放在 `MetadataInfo` 里面，否则消费者必须先拿到 metadata，才能知道去哪里拿
metadata，形成循环依赖。
解决方式就是把调用 MetadataService 所需的最小信息，直接写进注册中心的 `ServiceInstance.Metadata`。
**Provider 侧**
Provider 除了暴露业务接口 也会暴露框架内置接口
假设 Provider 导出的 MetadataService URL 是：
```text
tri://10.0.0.8:20880/org.apache.dubbo.metadata.MetadataService
?serialization=hessian2
&version=1.0.0
&application=demo-provider
×tamp=1786000000
```
注册中心里的服务实例已经包含：
```text
ServiceName = demo-provider
Host = 10.0.0.8
```
所以 customizer 只需要额外发布类似：
```json
{
"protocol": "tri",
"port": "20880",
"serialization": "hessian2",
"version": "1.0.0"
}
```
并存入：
```text
dubbo.metadata-service.url-params
```
**Consumer 侧**
消费者从 `ServiceInstance` 获得：
```text
Host = 10.0.0.8
ServiceName = demo-provider
URL Params = protocol、port、serialization、version
```
</details>
### Checklist
- [x] I confirm the target branch is `develop`
- [x] Code has passed local testing
- [x] I have added tests that prove my fix is effective or that my feature
works
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