Add OpenAI compatibility support and improve resource cleanup

- Introduced OpenAI compatibility configurations for external providers, enabling model alias routing via the OpenAI API format.
- Enhanced provider logic in `GetProviderName` to handle OpenAI aliases and added new helper functions for compatibility checks.
- Updated API handlers and client initialization to support OpenAI compatibility models.
- Improved resource cleanup across clients by closing response bodies and streams using deferred functions.

config.example.yaml

@@ -1,23 +1,29 @@
-# Server configuration
+# Server port
 port: 8317
+
+# Authentication directory (supports ~ for home directory)
 auth-dir: "~/.cli-proxy-api"
-debug: true
+
+# Enable debug logging
+debug: false
+
+# Proxy URL. Supports socks5/http/https protocols. Example: socks5://user:pass@192.168.1.1:1080/
 proxy-url: ""
 
-# Request retry times, if the response http code is 403, 408, 500, 502, 503, 504, it will retry
+# Number of times to retry a request. Retries will occur if the HTTP response code is 403, 408, 500, 502, 503, or 504.
 request-retry: 3
 
 # Quota exceeded behavior
 quota-exceeded:
-  switch-project: true
-  switch-preview-model: true
+  switch-project: true # Whether to automatically switch to another project when a quota is exceeded
+  switch-preview-model: true # Whether to automatically switch to a preview model when a quota is exceeded
 
-# API keys for client authentication
+# API keys for authentication
 api-keys:
-  - "12345"
-  - "23456"
+  - "your-api-key-1"
+  - "your-api-key-2"
 
-# Generative language API keys
+# API keys for official Generative Language API
 generative-language-api-key:
   - "AIzaSy...01"
   - "AIzaSy...02"
@@ -29,3 +35,14 @@ claude-api-key:
   - api-key: "sk-atSM..." # use the official claude API key, no need to set the base url
   - api-key: "sk-atSM..."
     base-url: "https://www.example.com" # use the custom claude API endpoint
+
+# OpenAI compatibility providers
+openai-compatibility:
+  - name: "openrouter" # The name of the provider; it will be used in the user agent and other places.
+    base-url: "https://openrouter.ai/api/v1" # The base URL of the provider.
+    api-keys: # The API keys for the provider. Add multiple keys if needed. Omit if unauthenticated access is allowed.
+      - "sk-or-v1-...b780"
+      - "sk-or-v1-...b781"
+    models: # The models supported by the provider.
+      - name: "moonshotai/kimi-k2:free" # The actual model name.
+        alias: "kimi-k2" # The alias used in the API.