Create NuGet package that when installed copies content to $(OutputPath) regardless of machine

I am trying to get a content file that is included with my NuGet package to be copied to the $(OutputPath) (in my case bin\Debug\netcoreapp3.1 where all the DLLs end up) of a target C# project when the target is built. This needs to work on developers' boxes and on build machines. Here's what I have so far.

I created a NuGet package project with a content node

<ItemGroup><Content Include="testsettings.json"><CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory></Content></ItemGroup>

I am using the default values for the pack target inputs IncludeContentInPack and ContentTargetFolders, which are true and content;contentFiles respectively.

When I build the package, I get the following structure where testsettings.json appears in contentFiles\any\netcoreapp3.1 and content folders of the .nupkg.

When I install the package into a target .csproj,

• the testsettings.json file is added to the project's root folder as expected
• the <PackageReference Include="..." Version="..."/> line is added to the target .csproj as expected
• no entry appears in the target .csproj for testsettings.json

When I build the target project, the DLLs go to $(OutputPath) but testsettings.json is not copied there, which makes sense because the default for a Content node's action is None). However, I need it to act like <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>.

I thought, "OK I will manually change testsettings.json using the Properties window to Copy if newer":

This adds a node to the target .csproj that looks like:

<ItemGroup><Content Update="C:\redacted\path\to\nuget\cache\package.name\N.N.N\contentFiles\any\netcoreapp3.1\testsettings.json"><CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory></Content></ItemGroup>

which works great for my machine. This will fail for any build machine and any other developer's machine because that path is specific to my machine.

How can I create the package so that when installing the package it will result in a repeatable way of getting testsettings.json in the right place?

In the course of researching this, I noticed that testhost.exe and testhost.dll somehow magically end up in the right spot even though their source NuGet package's .nuspec and structure are similar to mine. This has left me at bit of a loss on what I need to do to modify my NuGet package's .nuspec, .nupkg, build sequence, etc.

Preferable: Is there a way to do this, and if so how? Highly not preferable: Is there a manual change I can make in the target project such that I can get a reliable way of copying the file that works everywhere?