Document what's new in ASP.NET Core for .NET 9 Preview 2

[danroth27]

Update the "What's new in ASP.NET Core 9.0" for .NET 9 Preview 2

@adityamandaleeka @mkArtakMSFT Please have folks comment on this issue with the desired content.

FYI: @samsp-msft @JeremyLikness @mikekistler @claudiaregio @JamesNK @SteveSandersonMS @davidfowl

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Associated WorkItem - 212924

[mkArtakMSFT]

@javiercn can you please add a comment here about content that should go with the Constructor Injection work that you brought back? Thanks!

[mkArtakMSFT]

@javiercn and another one for the Blazorpack compression please.

[javiercn]

Constructor injection: It is now possible to inject dependencies via the constructor of a component instead of using @inject.

Blazor Web Server Components compression: Compression is now enabled by default for interactive server components. This comes with a restriction to framing the app within the same origin by default, which is achieved by a content-security policy. The compression settings as well as the framing behavior can be adjusted by passing a callback to AddInteractiveServerRenderMode

[guardrex]

I've also added primary ctors.

I've placed the guidance now (today, 3/1), and I note in the section headings "(Preview 2, mid-March)". I'll adjust that when Pre2 lands.

I see that multithreading has been pushing to Pre3. Let me know if there's anything else outside of compression and ctors. 👂

https://learn.microsoft.com/aspnet/core/release-notes/aspnetcore-9.0