Copy refactorings

[normanrz]

Description:

• Uses UPath(..., endpoint_url="..") instead of UPath(..., client_kwargs={"endpoint_url":".."}). This requires a change in Voxelytics.
• Adds more restrictions on fs-based mag copy
• The add_* methods in Attachments now return the created attachment objects, similar to add_layer and add_mag.

Todos:

• Updated Changelog

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
9967	8382	84%	80%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
webknossos/webknossos/cli/_utils.py	67%	🟢
webknossos/webknossos/cli/check_equality.py	89%	🟢
webknossos/webknossos/dataset/dataset.py	76%	🟢
webknossos/webknossos/dataset/layer/layer.py	86%	🟢
webknossos/webknossos/dataset/layer/segmentation_layer/attachments/attachments.py	86%	🟢
webknossos/webknossos/dataset/layer/view/_array.py	88%	🟢
webknossos/webknossos/dataset/layer/view/view.py	89%	🟢
webknossos/webknossos/utils.py	74%	🟢
TOTAL	82%	🟢

updated for commit: 61f4546 by action🐍

[normanrz]

There seems to be an issue on this branch with coverage reporting, which leads to a dirty repository in the CI. I need more time to debug this, so I extracted the conditional-write-disable into #1368.