Support using environment variables to configure username and passwords

[orf]

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• Added tests for changed code.
• Updated documentation for changed code.

As per #1871 you cannot configure HTTP basic auth using environment variables. This is a problem for a lot of use cases:

1. Docker - using build time secrets means you can inject the HTTP basic auth configuration as an environment and download packages from a private repository without including this information in the resulting container. That's harder to do if you execute poetry config ....

2. User onboarding - many companies inject credentials into laptops as environment variables, and tools should be configured to work with those with a minimum of configuration. Simply having POETRY_HTTP_BASIC_MY_INTERNAL_PYPI_USERNAME and POETRY_HTTP_BASIC_MY_INTERNAL_PYPI_PASSWORD should be sufficient.

[sdispater]

Thanks for you contribution.

However, this issue has already been handled in #1909 so I am closing this since it's a duplicate.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.