1. add update_doc to api which can udpate vector store from existed
content file
2. add parameter `delete_content` to delete_doc api. user can decide
whether delete local content file when delete doc.
3. fix bug in ApiReqeust.upload_doc
4. support listing docs existed in local folder bu not in db
1. make huggingfaceembeddings hashable
2. unify embeddings' loading method for all kbservie
3. make ApiRequest skip empty content when streaming json to avoid dict
KeyError