Add proxy_config documentation to Rust Server SDK (#2938)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: [email protected] <[email protected]>

Author: devin-ai-integration[bot]

docs/server-core/rust/_options.mdx

@@ -89,6 +89,13 @@ External data store for Statsig values.
 - **`global_custom_fields`**: Option\<HashMap\<String, DynamicValue\>\>
   Global custom fields to include with all evaluations.
 
+- **`proxy_config`**: Option\<ProxyConfig\>
+  Configuration for connecting through a proxy server. The `ProxyConfig` struct has the following properties:
+  - `proxy_host`: Option\<String\> - Specifies the proxy server host
+  - `proxy_port`: Option\<u16\> - Specifies the proxy server port
+  - `proxy_auth`: Option\<String\> - For proxy authentication (format: `"username:password"`)
+  - `proxy_protocol`: Option\<String\> - Specifies the protocol (e.g., `"http"`, `"https"`)
+
 
 ### Example Usage
 
@@ -115,9 +122,16 @@ let options = StatsigOptions::builder()
     .disable_all_logging(Some(false))
     .enable_id_lists(Some(true))
     .specs_sync_interval_ms(Some(30000))
+    // Configure proxy settings
+    .proxy_config(Some(ProxyConfig {
+        proxy_host: Some("proxy.example.com".to_string()),
+        proxy_port: Some(8080),
+        proxy_protocol: Some("https".to_string()),
+        proxy_auth: None, // Use Some("username:password".to_string()) if authentication is required
+    }))
     .build();
 
 // Pass the options object into Statsig::new()
 let statsig = Statsig::new("server-secret-key", Some(Arc::new(options)));
 statsig.initialize().await?;
-```
+```