[release/9.5] Multi-target RabbitMQ and Redis client libraries

[eerhardt]

Users encountered a NuGet downgrade error (NU1605) when using Aspire client library packages in .NET 9 projects.

This occurred because:

1. Component packages targeted only net8.0, which references Microsoft.Extensions.Hosting.Abstractions 8.0.1
2. They depend on Microsoft.Extensions.DependencyInjection.AutoActivation 9.9.0
3. AutoActivation 9.9.0 requires Microsoft.Extensions.Hosting.Abstractions >= 9.0.9
4. This created a downgrade conflict when the packages were consumed by .NET 9 projects

Contributes to #11888

Customer Impact

Users can get restore errors with our packages.

Testing

Manually ensured the new package restores clean.

Risk

Low to medium. We are adding a net9 TFM to our package, which we didn't have before. It shouldn't cause problems, but may.

Regression?

Yes

[Copilot]

Pull Request Overview

Purpose: Multi-target RabbitMQ and Redis component and test projects to include net9 (via $(AllTargetFrameworks)) and eliminate NuGet downgrade (NU1605) conflicts involving Microsoft.Extensions.Hosting.Abstractions.

• Replace single TargetFramework with TargetFrameworks across component and related test projects.
• Enable packaging of libraries for multiple TFMs to satisfy dependency version requirements in .NET 9.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/Aspire.StackExchange.Redis.Tests/Aspire.StackExchange.Redis.Tests.csproj	Multi-target test project to align with components and validate across all frameworks.
tests/Aspire.StackExchange.Redis.OutputCaching.Tests/Aspire.StackExchange.Redis.OutputCaching.Tests.csproj	Multi-target output caching Redis tests for net9 compatibility.
tests/Aspire.StackExchange.Redis.DistributedCaching.Tests/Aspire.StackExchange.Redis.DistributedCaching.Tests.csproj	Multi-target distributed caching Redis tests.
tests/Aspire.RabbitMQ.Client.v7.Tests/Aspire.RabbitMQ.Client.v7.Tests.csproj	Multi-target RabbitMQ v7 client tests for expanded TFM coverage.
tests/Aspire.RabbitMQ.Client.Tests/Aspire.RabbitMQ.Client.Tests.csproj	Multi-target RabbitMQ v6 client tests; retains RABBITMQ_V6 define constant.
src/Components/Aspire.StackExchange.Redis/Aspire.StackExchange.Redis.csproj	Multi-target Redis client component for proper dependency resolution.
src/Components/Aspire.StackExchange.Redis.OutputCaching/Aspire.StackExchange.Redis.OutputCaching.csproj	Multi-target Redis Output Caching component.
src/Components/Aspire.StackExchange.Redis.DistributedCaching/Aspire.StackExchange.Redis.DistributedCaching.csproj	Multi-target Redis Distributed Caching component.
src/Components/Aspire.RabbitMQ.Client/Aspire.RabbitMQ.Client.csproj	Multi-target RabbitMQ client component.
src/Components/Aspire.RabbitMQ.Client.v7/Aspire.RabbitMQ.Client.v7.csproj	Multi-target RabbitMQ v7 client component.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 12138

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 12138"