Add Digital Ocean storage flavor

[guilload]

Description

• Add Digital Ocean storage flavor
• Fix MinIO flavor

How was this PR tested?

• Added unit tests
• Run the following integrating test on Digital Ocean:

fn test_suite_on_s3_storage_path_style_access() {
    let s3_storage_config = S3StorageConfig {
        force_path_style_access: true,
        disable_multi_object_delete: true,
        ..Default::default()
    };
    let bucket_uri = append_random_suffix("s3://quickwit-integration-tests/test-path-style-access");
    let test_runtime = test_runtime_singleton();
    test_runtime.block_on(run_s3_storage_test_suite(s3_storage_config, &bucket_uri));
}

AWS_PROFILE=do \
AWS_REGION=nyc3 \
QW_S3_ENDPOINT=https://quickwit-integration-tests.nyc3.digitaloceanspaces.com \
cargo test --manifest-path quickwit/Cargo.toml -p quickwit-storage --all-features -- test_suite_on_s3_storage_path_style_access

[trinity-1686a]

LGTM. Could you also update docs/configuration/node-config.md with the new flavor?