ASP.NET Core updates in .NET 9 Preview 1

[danroth27]

Here's a summary of what's new in ASP.NET Core in this preview release:

• Dictionary debugging improvements
• Polymorphic type support in SignalR Hubs
• General quality improvements and bug fixes

ASP.NET Core updates in .NET 9 Preview 1:

• Release notes
• What's new in ASP.NET Core in .NET 9 documentation.
• Breaking changes
• Roadmap

.NET 9 Preview 1:

• Discussion
• Release notes