Check for group of repeated arguments

[Velnbur]

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• I have searched the discussions
• I have searched the open and rejected issues

Clap Version

4.3.23

Describe your use case

Currently trying to implement a CLI that accepts different repeated arguments. The problem is that we need to add checks that the lengths of a subset of repeated parameters should be the same.

1. So for example CLI sends different messages to different recipients:

# is okay
cli send --recipient ALICE --content "hi!" --recipient BOB --content "goodbye"
# results in error as no second recipient is presented
cli send --recipient ALICE --content "hi!" --content "goodbye"

2. But recipients.len() < contents.len() is okay:

cli send --recipient ALICE --recipient BOB --content "hi!"

Just the same content will be sent to different recipients. So contents became vec!["hi!"; recipients.len()] in this case.

Describe the solution you'd like

Developing additional functionality to ArgGroup could fix that, but I have no context about its current implementation.

Alternatives, if applicable

I believe that #1704 will fix the first case of the requested feature. Which, with some additional tweaks, can fulfill my needs with second case too

Additional Context

No response