Default Bootstrap version of IdentityUI changed to 4

[ryanbrandenburg]

Currently the default version of Bootstrap for IdentityUI is UIFramework.Bootstrap3, but starting in 3.0.0-preview4 the default will be UIFramework.Bootstrap4. We think this better reflects our recomendation that new projects use Bootstrap4.

You will be affected by this change if you use IdentityUI but do not explicitly set a UIFramework. There are two ways to resolve this:

1. Move your project to Bootstrap4.
2. Explicitly set your project to Bootstrap3 by calling services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(UIFramework.Bootstrap3).

Use issue: aspnet/AspNetCore#9516 for discussion.

[This announcement has been migrated to: dotnet/docs#14882]