Enable custom storage providers for ASP.NET Core Identity

[tedvanderveen]

See for ref:

• https://docs.microsoft.com/en-us/aspnet/core/security/authentication/identity-custom-storage-providers?view=aspnetcore-5.0
• https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/security/authentication/identity-custom-storage-providers/sample/CustomIdentityProviderSample

At the moment, the Piranha.AspNetCore.Identity package has a dependency on Microsoft.EntityFrameworkCore:

piranha.core/identity/Piranha.AspNetCore.Identity/IDb.cs

Line 15 in fe7fd28

using Microsoft.EntityFrameworkCore;

But what if one does not want to store user and role data in a relational database? Like in my customer's case, we would like to reuse the existing user and role management and UI/Razor features (https://github.com/PiranhaCMS/piranha.core/tree/master/identity/Piranha.AspNetCore.Identity/Areas/Manager/Views), but bring our own custom Identity storage provider.

Possible way of setting this up, is the creation of a new package Piranha.AspNetCore.Identity.EntityFrameworkCore that provides the EF implementations of IRoleStore and IUserStore. And remove any dependency on Microsoft.EntityFrameworkCore from the Piranha.AspNetCore.Identity package?

As an additional bonus, we can include a file based IRoleStore and IUserStore implementation to the Piranha.AspNetCore.SimpleSecurity package for demo/testing setups.

I would be very happy to further investigate this and submit a PR if this issue and described approach is okay for you guys.