Add batch_size in config for VectorDB (#1448)

tests/vectordb/test_weaviate.py

@@ -124,7 +124,7 @@ class TestWeaviateDb(unittest.TestCase):
         db = WeaviateDB()
         app_config = AppConfig(collect_metrics=False)
         App(config=app_config, db=db, embedding_model=embedder)
-        db.BATCH_SIZE = 1
+        db.config.batch_size = 1
 
         documents = ["This is test document"]
         metadatas = [None]