poetry build-system uses outdated API

[ohnomydjango]

When setting this repo up locally in editable mode to use with another app, I had to change the build-system in pyproject.toml from:

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"

to:

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

This probably needs updating at the project level but that was out-of-scope for what I was doing.