EF Core DB First Documentation

I think it is must be written here that for EF Core user that using DB first approach, we must create the DataProtectionKeys table manually, and the Id column also must be an IDENTITY column too.

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#### Document Details

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* ID: 59850a13-1322-0c54-9fd3-75ce837c2b1a
* Version Independent ID: 7d481dae-d27d-909c-a35d-bad66c7508d2
* Content: [Key storage providers in ASP.NET Core](https://docs.microsoft.com/en-us/aspnet/core/security/data-protection/implementation/key-storage-providers?view=aspnetcore-3.1&tabs=visual-studio#entity-framework-core)
* Content Source: [aspnetcore/security/data-protection/implementation/key-storage-providers.md](https://github.com/dotnet/AspNetCore.Docs/blob/master/aspnetcore/security/data-protection/implementation/key-storage-providers.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-security**
* GitHub Login: @Rick-Anderson
* Microsoft Alias: **riande**