idtools: return errors for >u32 specification

[cyphar]

This isn't a huge issue, but it could cause user confusion if they provide too large a value.

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 73.70%. Comparing base (71d012d) to head (e597e6a). Report is 3 commits behind head on main.

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Additional details and impacted files

[](https://app.codecov.io/gh/opencontainers/umoci/pull/558?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opencontainers) ```diff @@ Coverage Diff @@ ## main #558 +/- ## ========================================== + Coverage 73.68% 73.70% +0.01% ========================================== Files 60 60 Lines 4903 4906 +3 ========================================== + Hits 3613 3616 +3 Misses 941 941 Partials 349 349 ``` | [Files with missing lines](https://app.codecov.io/gh/opencontainers/umoci/pull/558?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opencontainers) | Coverage Δ | | |---|---|---| | [pkg/idtools/idtools.go](https://app.codecov.io/gh/opencontainers/umoci/pull/558?src=pr&el=tree&filepath=pkg%2Fidtools%2Fidtools.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=opencontainers#diff-cGtnL2lkdG9vbHMvaWR0b29scy5nbw==) | `100.00% <100.00%> (ø)` | |