feat(alibaba): support custom endpoint in OSSHook for VPC internal access

[wenbinye]

Summary

OSSHook._get_client now reads extra.endpoint from the connection config, enabling VPC internal endpoints (e.g. oss-cn-hangzhou-internal.aliyuncs.com) instead of being limited to public endpoints.

Motivation

When Airflow pods run in the same VPC as Alibaba Cloud OSS, using the public endpoint incurs unnecessary public traffic. For clusters in the same region, the VPC internal endpoint (oss-{region}-internal.aliyuncs.com) provides lower latency and no egress charges.

Changes

• oss.py: _get_client now checks for extra.endpoint before falling back to the default public endpoint
• test_oss.py: Added test_get_client_default_endpoint and test_get_client_custom_endpoint
• oss_mock.py: Updated mock_oss_hook_default_project_id to accept optional endpoint parameter

How to use

Set endpoint in the extra field of the OSS connection:

{
  "auth_type": "AK",
  "access_key_id": "...",
  "access_key_secret": "...",
  "region": "cn-hangzhou",
  "endpoint": "oss-cn-hangzhou-internal.aliyuncs.com"
}

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

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