docs: Update OPA Policy Configuration with Example (#12840)

Author: YapWC

docs/en/latest/plugins/opa.md

@@ -38,7 +38,7 @@ The `opa` Plugin can be used to integrate with [Open Policy Agent (OPA)](https:/
 |-------------------|---------|----------|---------|---------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | host              | string  | True     |         |               | Host address of the OPA service. For example, `https://localhost:8181`.                                                                                                                    |
 | ssl_verify        | boolean | False    | true    |               | When set to `true` verifies the SSL certificates.                                                                                                                                          |
-| policy            | string  | True     |         |               | OPA policy path. A combination of `package` and `decision`. While using advanced features like custom response, you can omit `decision`.                                                   |
+| policy            | string  | True     |         |               | OPA policy path. A combination of `package` and `decision`. While using advanced features like custom response, you can omit `decision`. When specifying a namespace, use the slash format (`examples/echo`) instead of dot notation (`examples.echo`).  |
 | timeout           | integer | False    | 3000ms  | [1, 60000]ms  | Timeout for the HTTP call.                                                                                                                                                                 |
 | keepalive         | boolean | False    | true    |               | When set to `true`, keeps the connection alive for multiple requests.                                                                                                                      |
 | keepalive_timeout | integer | False    | 60000ms | [1000, ...]ms | Idle time after which the connection is closed.                                                                                                                                            |

docs/zh/latest/plugins/opa.md

@@ -38,7 +38,7 @@ description: 本篇文档介绍了 Apache APISIX 通过 opa 插件与 Open Polic
 |-------------------|---------|----------|---------|---------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | host              | string  | 是     |         |               | OPA 服务的主机地址，例如 `https://localhost:8181`。                                                                                                                   |
 | ssl_verify        | boolean | 否    | true    |               | 当设置为 `true` 时，将验证 SSL 证书。                                                                                                                                          |
-| policy            | string  | 是     |         |               | OPA 策略路径，是 `package` 和 `decision` 配置的组合。当使用高级功能（如自定义响应）时，你可以省略 `decision` 配置。                                                  |
+| policy            | string  | 是     |         |               | OPA 策略路径，是 `package` 和 `decision` 配置的组合。当使用高级功能（如自定义响应）时，你可以省略 `decision` 配置。指定命名空间时，请使用斜杠格式（例如 `examples/echo`），而不是点号格式（例如 `examples.echo`）。        |
 | timeout           | integer | 否    | 3000ms  | [1, 60000]ms  | 设置 HTTP 调用超时时间。                                                                                                                                                                |
 | keepalive         | boolean | 否    | true    |               | 当设置为 `true` 时，将为多个请求保持连接并处于活动状态。                                                                                                                               |
 | keepalive_timeout | integer | 否    | 60000ms | [1000, ...]ms | 连接断开后的闲置时间。                                                                                                                                                                        |