Struct BrokerAuthRequest 

pub struct BrokerAuthRequest<'a> {
    pub http: &'a Client,
    pub protocol_identity: BackendProtocolIdentity,
    pub uid: u64,
    pub broker_id: u32,
    pub auth_code: &'a str,
    pub device_id: &'a str,
    pub web_tcp_identity: u32,
    pub web_tcp_addrs: &'a [(String, u16)],
    pub site_config: Option<&'a SharedSiteConfig>,
    pub auth_guaranteed_domains: &'a AuthGuaranteedDomainMap,
    pub auth_guaranteed_domains_configured: bool,
    pub route_cache: Option<&'a BrokerAuthRouteCache>,
}

向 broker auth 域名发 /broker_auth/client_auth POST 请求，换取 broker_client_sig + broker_client_key。

对齐 C++ auth_impl.cpp:640-674（RefreshBrokerClientSig）+ auth_impl.cpp:3378-3480（ParseBrokerAuthResponse）：

• URL：POST https://{broker_auth_domain}/broker_auth/client_auth
• Body：{"uid", "auth_code", "device_id", "broker_id"}
• 响应 result 里的 broker_client_key 是 base64 编码 + AES-CBC-MD5 加密过的

⚠️ 解密不是用 rand_key！对齐 auth_impl.cpp:3434 —— 该处调用 DecryptByRandKey(&broker_client_key, nullptr)，nullptr 触发 auth_cryptor.cpp:324-332 分支：用固定默认 key 解密（先试 AES-256， 失败兜底 AES-128），不是 Platform client_key 用的 rand_key。 具体 response/error/decrypt 逻辑由 sibling broker::response adapter 持有。

Fields

http: &'a Client

protocol_identity: BackendProtocolIdentity

uid: u64

broker_id: u32

auth_code: &'a str

device_id: &'a str

web_tcp_identity: u32

web_tcp_addrs: &'a [(String, u16)]

site_config: Option<&'a SharedSiteConfig>

auth_guaranteed_domains: &'a AuthGuaranteedDomainMap

auth_guaranteed_domains_configured: bool

route_cache: Option<&'a BrokerAuthRouteCache>