Author output frequently broken for packages using pyproject.toml metadata

[dgw]

This is a specific case of #7 that is so important as to warrant its own issue.

Declaring authorship metadata in a package using pyproject.toml often causes this plugin to output "(unknown author)", due to how the metadata is parsed and exposed by Warehouse (PyPI). For example, this TOML metadata:

authors = [
  { name="dgw", email="dgw@notmyrealemail.tld" }
]

turns into JSON like:

{
  "info": {
    "author": null,
    "author_email": "dgw \u003Cdgw@notmyrealemail.tld\u003E",

The information we want is contained in the author_email field, but since the author's name is null, sopel-pypi treats it as unknown. Unfortunately the information we want is mixed in with information we don't want.

Have been hoping for pypi/warehouse#9400 to get resolved, but it's taking too long. I'd like this plugin to have useful output for packages using the newer metadata standards sooner than the timeline on which PyPI seems inclined to fix this.