# group

## get_group_root_folder
### params
'username', 'token', 'group_id'
### return
- code=401, error='未登录'
- code=403, error='群不存在'
- code=200, root_folder_id

## join_group
### params
'username', 'token', 'group_id'
### return
- code=401, error='未登录'
- code=402, error='已在群内'
- code=403, error='群不存在'
- code=200

## create_group
### params
'username', 'token', 'group_name'
### return
- code=401, error='未登录'
- code=500, error='新建群失败'
- code=200

## quit_group
### params
'username', 'token', 'group_id'
### return
- code=401, error='未登录'
- code=403, error='群不存在'
- code=421, error='群主不可退群'
- code=200

## group_list
### params
'username', 'token'
### return
- code=200, group_list