fix: use xarray.Dataset copy instead of constructor

[maurerle]

minimal non-working example:

import pypsa
network = pypsa.examples.ac_dc_meshed()
network.optimize()

Changes proposed in this Pull Request

since the latest xarray version, passing a Dataset as data_vars to the Dataset constructor is not supported. Use ds.copy() to create a copy of a Dataset.

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the MIT license.

[FBumann]

Im not sure if we should exclude highspy==1.14.0 from linopy deps. This PR gets the CI working, but users will get wring results with highs. Not fully our responsibility, but worth considering

[coroa]

Im not sure if we should exclude highspy==1.14.0 from linopy deps. This PR gets the CI working, but users will get wring results with highs. Not fully our responsibility, but worth considering

Yes, we should, but not in this PR.

[maurerle]

The CI does not run through because of missing #654

[FBumann]

Suggested change

# Wrapping an existing Dataset in Dataset(...) is no longer supported

Remove this explanation. After we merge this it adds nothing. Its more like a commit message

[FBumann]

Suggested change

# by newer xarray versions.

Remove this explanation. After we merge this it adds nothing. Its more like a commit message

[coroa]

Ok, thanks. I'll see if i can get a release out today or latest on Monday.