Support Alicloud OSS

[niejn]

Title

Support Alicloud OSS

Motivation

I am currently working for alibaba, and I encounter marvelous smartopen lib when I am coding. However, it doesn't support Alicloud OSS.
So I figured I should add oss support myself.
Contributing to opensource community is always my dream.

Tests

still working on integration tests.

Work in progress

70% finished, would love to hear your comments.

Checklist

Before you create the PR, please make sure you have:

• Picked a concise, informative and complete title
• Clearly explained the motivation behind the PR
• Linked to any existing issues that your PR will be solving
• Included tests for any new functionality
• Checked that all unit tests pass

[mpenkov]

Hi, had a brief look at the changes, looks like you're on the right track. Let me know when the code is ready for a review. Thanks!

[feisan]

Any updates?

[ddelange]

Accessing Alibaba Cloud OSS using boto3 is officially supported meaning you can also use boto3's automatic credential discovery like smart_open usually does:

import boto3
from botocore.config import Config

oss_client = boto3.client(
    's3',
    endpoint_url='https://s3.oss-cn-hongkong.aliyuncs.com',
    config=Config(
        signature_version='s3',  # no chunked encoding
        s3={"addressing_style": "virtual"},
        # may be required for boto3 >= 1.36.0 with third-party S3
        # https://github.com/boto/boto3/issues/4400#issuecomment-2600742103
        request_checksum_calculation='when_required',
        response_checksum_validation='when_required',
    )
)

transport_params = {'client': oss_client}

with open(f's3://bucket/test.txt', 'r', transport_params=transport_params) as fin:
    print("smart_open read success:")

With this MWE, I'll close this PR, analogous to #824 and other third party s3-compatible storage systems.