8.7.4: Add support for Poetry 1.2.0+'s dependency groups

[tiegz]

Poetry 1.2.0 added support for dependency groups in python-poetry/poetry#4260 , e.g.:

[tool.poetry.group.test.dependencies]
pytest = "^6.0.0"
pytest-mock = "*"

docs: https://github.com/python-poetry/poetry/blob/1.7.1/docs/managing-dependencies.md#dependency-groups

[tiegz]

this ensures that pypoetry.lock should not get a type: nil back

[mikeyoung85]

We should add another group here and test that the type works correctly. Something like [tool.poetry.group.test.dependencies].

[mikeyoung85]

I'm familiar with toml and how these are getting parsed. What would the expected group names look like. From the Poetry example what would the group_name for [tool.poetry.group.test.dependencies] resolve to here?

[tiegz]

AFAICT it'll use the name that was parsed, so test would be the group there. The docs say:

use a tool.poetry.group. section where is the name of your dependency group (for instance, test):

There's an implicit main group that is the default, but we've apparently mapped that to runtime until now so I'm setting that as the default in the change below.

Also noteworthy is that anything that's not main is considered development semantically, so there's no real distinction between dev and test to Poetry other than the names:

Dependency groups, other than the implicit main group, must only contain dependencies you need in your development process. Installing them is only possible by using Poetry.

And FWIW, I'd prefer that Bibliothecary return "development" here to be consistent with the other parsers, but there are 3 uses of "develop" in this file so I'm hesitant to break anything for consumers of the gem : \