Remove expire argument for url method and do not generate signed url for public/public-read bucket

[jxltom]

• Trying to solve python manage.py collectstatic run error！ #2 TypeError: url() missing 1 required positional argument: 'expire' #9. url method is not compatible with django's default Storage class since it should has only one required positional argument.

  • Environment variable OSS_EXPIRE_TIME in seconds can be set for url expire time.

  • If OSS_EXPIRE_TIME is not set, default value is 60*60*24*30 which is 30 days will be used.

• For public/public-read bucket, there is no need to use signed urls since it will generate unique url (Signature parameter in url will change each time) each time. This makes CDN or brower cache unavailable. Since OSS ususally serves as static/media file serving purpose, it is better to use constant urls for public/public-read buckets.

[CLAassistant]

All committers have signed the CLA.

[tiany]

没人在维护吗？这么严重的Bug 5个月了还没合入的说 =。=

[huiguangjun]

已经根据 修改内容 合入到 dev-1911 分支

[jxltom]

Same with #11, why this PR is merged without my author information 😢

[tiany]

Because they made the same changes instead of merge your PR... Quite interesting.