bug: unauthorized access in Alicloud OSS component

[seeflood]

What happened:
If an app pass a directoryName which is not configurated in the config file,it can access that bucket although it shouldn't.
Currently the code doesn't do the access control checking.

What you expected to happen:
Forbid unauthorized access

How to reproduce it (as minimally and precisely as possible):
@fengmk2 found it by code review

Anything else we need to know?:

[ZLBer]

@seeflood alicloud/aws/minio components both have this problem. I'll fix this .
The meaning of the bukect field is not clearly stated in the fileAPI qucick start file, a little fuzzy,

_sidebar.md quick start lack fileAPI.

[seeflood]

@seeflood alicloud/aws/minio components both have this problem. I'll fix this .

Sorry for not explaining in advance, @wenxuwan just told me that he is working on it and decides to remove this bucket configuration and do some refactor for File API. So this issue will be assigned to him.
Actually the accessKeyID and accessKeySecret fields are enough to do access control,so the bucket field is redundant.
Hope he will add a quickstart for File API after the refactor :)

[ZLBer]

@seeflood Okay, I get it

[wenxuwan]

@ZLBer Hi man, as the current file interface capabilities are not enough to support users,#98, I am redesigning the interface and modifying the implementation, you can help review it together.#305