feat(main.py): support router.chat.completions.create

allows using router with instructor

https://github.com/BerriAI/litellm/issues/2673

litellm/main.py

@@ -116,24 +116,54 @@ class LiteLLM:
         default_headers: Optional[Mapping[str, str]] = None,
     ):
         self.params = locals()
-        self.chat = Chat(self.params)
+        self.chat = Chat(self.params, router_obj=None)
 
 
 class Chat:
-    def __init__(self, params):
+    def __init__(self, params, router_obj: Optional[Any]):
         self.params = params
-        self.completions = Completions(self.params)
+        if self.params.get("acompletion", False) == True:
+            self.params.pop("acompletion")
+            self.completions: Union[AsyncCompletions, Completions] = AsyncCompletions(
+                self.params, router_obj=router_obj
+            )
+        else:
+            self.completions = Completions(self.params, router_obj=router_obj)
 
 
 class Completions:
-    def __init__(self, params):
+    def __init__(self, params, router_obj: Optional[Any]):
         self.params = params
+        self.router_obj = router_obj
 
     def create(self, messages, model=None, **kwargs):
         for k, v in kwargs.items():
             self.params[k] = v
         model = model or self.params.get("model")
-        response = completion(model=model, messages=messages, **self.params)
+        if self.router_obj is not None:
+            response = self.router_obj.completion(
+                model=model, messages=messages, **self.params
+            )
+        else:
+            response = completion(model=model, messages=messages, **self.params)
+        return response
+
+
+class AsyncCompletions:
+    def __init__(self, params, router_obj: Optional[Any]):
+        self.params = params
+        self.router_obj = router_obj
+
+    async def create(self, messages, model=None, **kwargs):
+        for k, v in kwargs.items():
+            self.params[k] = v
+        model = model or self.params.get("model")
+        if self.router_obj is not None:
+            response = await self.router_obj.acompletion(
+                model=model, messages=messages, **self.params
+            )
+        else:
+            response = await acompletion(model=model, messages=messages, **self.params)
         return response