False positive for empty author / maintainer item

[abelcheung]

Following schema is vaildated as correct, but shouldn't have been:

[project]
name = 'foo'
version = '1.0'
authors = [{}]

Packaging specification contains the following sentence:

Both keys are optional, but at least one of the keys must be specified in the table.

But bundled schema specifies both keys as optional without requiring any key:

validate-pyproject/src/validate_pyproject/project_metadata.schema.json

Lines 310 to 329 in db197f4

	"author": {
	"$id": "#/definitions/author",
	"title": "Author or Maintainer",
	"$comment": "https://peps.python.org/pep-0621/#authors-maintainers",
	"type": "object",
	"additionalProperties": false,
	"properties": {
	"name": {
	"type": "string",
	"$$description": [
	"MUST be a valid email name, i.e. whatever can be put as a name, before an",
	"email, in :rfc:`822`."
	]
	},
	"email": {
	"type": "string",
	"format": "idn-email",
	"description": "MUST be a valid email address"
	}
	}