feat: support minio credentials for datasets

[tanmaykm]

Handle minio credentials for dataset operations.

fixes: https://github.com/JuliaComputing/JuliaHub/issues/20486

requires: #108

[tanmaykm]

Looks like CI is failing because of changes needed in test code for v2 job images. I'll try to add some commits here to fix them, but then migrate it to a separate PR so that they are grouped properly.

[tanmaykm]

Opened #108 with the updates required for v2 images

[mortenpi]

Just one small code structure request. Other than that, I think this needs:

• A changelog entry.
• A note in the docs, probably on the datasets reference page, that JuliaHub instances using Minio need at least JuliaHub.jl 0.1.16.