Duplicate NuGetAuditSuppress warnings use code NU1508

[zivkan]

Bug

Fixes: NuGet/Home#13620

Description

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc. Add docs for NU1508 Home#13621

[zivkan]

@nkolev92 why does NuGet.exe disable duplicate checking?

NuGet.Client/src/NuGet.Clients/NuGet.CommandLine/MsBuildUtility.cs

Line 265 in 128a506

AddProperty(args, "DisableCheckingDuplicateNuGetItems", bool.TrueString);

[nkolev92]

Because TreatWarningsAsErrors would fail the dg spec generation and fail the operation with a message that's not very actionable.
It wasn't worth the effort back then.

Spec has more details: https://github.com/NuGet/Home/blob/dev/accepted/2022/duplicate-nuget-item-error-handling.md#technical-explanation.

[zivkan]

@nkolev92 from NuGet/Home#13620

This should be a new log code.

Why do we use a different code for each MSBuild item type?

The docs are the same for each item type, since the resolution is the same. I feel like all this design decision does is cause us extra busy work. I feel like one error code, where in the docs we mention that this can happen for multiple item types, would just be easier, with no downside.

[nkolev92]

The owner of the action isn't always the same.
In particular the SDK sets PackageDownload items, so any issues are likely problems on the SDK side.

For example, if you search with NU1505, you end up with dotnet/sdk#24747.
NU1504 gives you something else.

It's duplicative sure, but I think there's an eventual limit to the number of items we'll be using :)