No integration test coverage for object-storage code path

### Describe the bug

Code paths for object-storages like S3, GCS or Azure do not have integration test coverage.

At a very minimum, the following needs integration testing:
* S3 against Minio + STS/IAM
* GCS against e.g. fake-gcs-server
* Azure against e.g. Azurite

### To Reproduce

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### Actual Behavior

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### Expected Behavior

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### Additional context

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### System information

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Start by locating the object-storage code paths and the repository's existing integration-test setup. Add coverage for S3 with Minio plus STS/IAM, GCS with fake-gcs-server, and Azure with Azurite; the work is done when these provider paths have passing integration tests.

Written by the indexing model from the issue text.