Expand capbilities of `upload_project_dataset` to match those of `upload_dataset`

[korsbo]

Hi,

I'm building some simple utils for easier sharing of results and datasets within a project. I like how the JuliaHub "project" lets multiple users update the dataset, but I'm still running into a few API snags when doing this programmatically. A key issue is that upload_project_dataset fails when uploading a new dataset (at least when supplying the project UUID directly rather than having it in authenticate). Right now, I have to use upload_dataset and then manually go to the web UI to link the dataset to the project and enable writability.

The following upload_project_dataset enhancements would make it a lot more usable:

• support for adding new datasets.
• kwarg for setting "Enable writability"
• tag and description kwarg, and just feature parity with upload_dataset.

Thanks!