• I have searched the issues of this repo and believe that this is not a duplicate.
• I have searched the documentation and believe that my question is not covered.

Feature Request

It would be handy to have a flag like --all-extras to install every package listed in any of the extras.

The specific use case is that I want the IDE to index the packages for every subsystem (AWS Lambda jobs in this case) for easier development.

Workarounds:

1. Creating a separate "extra" section with all the packages from all the other extras (example). This means duplication, which means it would be really easy for the sections to get out of sync.
2. Listing each extra specifically in the developer instructions.
3. This ugly code, used in anger here: poetry install --extras="$(sed --quiet '/\[tool\.poetry\.extras\]/,/^\[/{s/^\(.*\) = \[/\1/p}' pyproject.toml | sed --null-data 's/\n/ /g;s/ $//')" --remove-untracked