Add support for poetry v2

[DBS-ST-VIT]

Hey @ajkerrigan,
this maybe solves #26.

Actually, we implemented it with legacy support for poetry 1.x.x, but thats something we can also remove. We thought, that it is may be more user friendly with some time with legacy support. Maybe we should also add a deprecation notice for usage with poetry 1.x.x?

Further, there was one deprecation (see here) which has been fixed by actually adapting the current code from poetry. For us, this doesn't look like the best solution, but poetry-plugin-export is expecting a BaseMarker object, which is the reason why we need to work with the marker here and cannot use e.g. the .python_constraint property instead.

[ajkerrigan]

I'm generally good with this, the v2 changes don't look bad at all. Your handling of the python_marker change looks good 👍 .

A couple other comments/suggestions inline related to the upstream rename of PyProjectException --> PyProjectError and how to gracefully handle that.

[DBS-ST-VIT]

Hey @ajkerrigan,
many thanks for your input! I updated the branch in our forked repo according your suggestions and also cleaned a little bit up.

May you can have a look on it?

[WhoAmI0501]

Hi @ajkerrigan ,
i am also waiting for this PR for upgrading to poetry v2. This is the last poetry plugin in my collection that is lacking v2 support. Can you merge this PR?

[RudolfVonKrugstein]

Oh, this would be cool! I want to upgrade to poetry V2, but need this plugin.

[ajkerrigan]

I'm good with these changes, pushed one minor tweak to make sure we're covering the PyProjectException/PyProjectError/RuntimeError cases. Thanks for working on this one @DBS-ST-VIT 👍