Update src/Security/samples from using Startup to .NET 8 or higher

[Rick-Anderson]

All the security samples use startup. It would be nice to have them updated to .NET 10.

cc @martincostello

[samabos]

Hi @Rick-Anderson, I recommend submitting one PR per project in the sample folder to make code reviews easier and faster.

[samabos]

Also, if we're good to go, I can start with the CustomPolicyProvider sample project and submit a PR.

[MackinnonBuck]

@Rick-Anderson, are these samples being linked to from docs? These are intended for internal development purposes only. They use the same TargetFramework as the rest of the aspnetcore repo (currently .NET 10), even if they don't use the latest .NET 10 APIs. Is this a problem?

[Rick-Anderson]

@Rick-Anderson, are these samples being linked to from docs? These are intended for internal development purposes only. They use the same TargetFramework as the rest of the aspnetcore repo (currently .NET 10), even if they don't use the latest .NET 10 APIs. Is this a problem?

That was my intention until I found out they're not meant for the docs, so I closed the doc issue.

[MackinnonBuck]

Thanks, @Rick-Anderson. Closing out this issue as well then.