fix: Remove duplicated parts

src/ai/backend/common/api_handlers.py

@@ -267,23 +267,18 @@ def api_handler(handler: BaseHandler) -> ParsedRequestHandler:
 
     1. Request Body:
         @api_handler
-        @api_handler
-        # UserModel is a Pydantic model
-        async def handler(body: BodyParam[UserModel]):
-            # 'parsed' property gets pydantic model you defined
-            user = body.parsed
+        async def handler(body: BodyParam[UserModel]):  # UserModel is a Pydantic model
+            user = body.parsed                          # 'parsed' property gets pydantic model you defined
             # Response model should inherit BaseResponseModel
             return APIResponse.build(status_code=200, response_model=YourResponseModel(user=user.id))
 
     2. Query Parameters:
-        @api_handler
         @api_handler
         async def handler(query: QueryParam[QueryPathModel]):
             parsed_query = query.parsed
             return APIResponse.build(status_code=200, response_model=YourResponseModel(search=parsed_query.query))
 
     3. Headers:
-        @api_handler
         @api_handler
         async def handler(headers: HeaderParam[HeaderModel]):
             parsed_header = headers.parsed
@@ -308,13 +303,10 @@ def from_request(cls, request: web.Request) -> Self:
                 return cls(user_id=user_id)
 
         @api_handler
-        @api_handler
-        # No generic, so no need to call 'parsed'
-        async def handler(auth: AuthMiddlewareParam):
+        async def handler(auth: AuthMiddlewareParam):   # No generic, so no need to call 'parsed'
             return APIResponse(status_code=200, response_model=YourResponseModel(author_name=auth.name))
 
     6. Multiple Parameters:
-        @api_handler
         @api_handler
         async def handler(
             user: BodyParam[UserModel],  # body