.NET 8 update: Introduction to Identity to minimal hosting

#23272 did much of it. Need scaffolding updates to complete.

See [all issues for this doc](https://github.com/dotnet/AspNetCore.Docs/issues?q=is%3Aissue+is%3Aopen+0e0d870e-e49a-e16c-c259-68d58e701b8f)

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#### Document Details

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* ID: 94bfd895-d2af-390b-0801-428b36a27ff4
* Version Independent ID: 0e0d870e-e49a-e16c-c259-68d58e701b8f
* Content: [Introduction to Identity on ASP.NET Core](https://docs.microsoft.com/en-us/aspnet/core/security/authentication/identity)
* Content Source: [aspnetcore/security/authentication/identity.md](https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/security/authentication/identity.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-security**
* GitHub Login: @Rick-Anderson
* Microsoft Alias: **riande**