Support poetry install --only

Feature Request

Currently the script PythonBashBuildSnippet.sh.tpl assumes that pyproject.toml implies that the user always intends to use 'poetry run --no-env'. First of all, 'poetry install --no-env' is deprecated (https://python-poetry.org/docs/cli/#install) in favor of, for example, poetry install --only no-dev. Secondly we have a use case where we deploy a monorepo containing many dependencies using github actions to an Azure App, which uses Oryx as the build system. We have a smaller dependency group defined in the pyproject.toml, which contains only the dependencies that are needed to the deployed application. So, in this case, what we would like to run is poetry install --only on this subset of dependencies.

It would be nice if we can set an environment variable that allows to specify additional poetry install arguments. The documentation makes no mention of this and the PythonBashBuildSnippet.sh.tpl seems to indicate that this is not an option.

I think this would be a useful feature to support for users who deploy an entire monorepo, but only wish to run a specific package from that monorepo as an Azure App.