Redress cookie name

[JunTaoLuo]

#763

As part of fixing MusicStore tests in aspnet/MusicStore#601, @natemcmaster found that we are not setting the cookie names correctly for cookies used by Identity. The reason for this is in the referenced issue.

cc @Tratcher @HaoK

[HaoK]

What happened to the AspNetCore?

[JunTaoLuo]

@HaoK It is added by default by CookieAuthentication at https://github.com/aspnet/Security/blob/a5b288897d2981c241133b8d37aa22136b653e3a/src/Microsoft.AspNetCore.Authentication.Cookies/CookieAuthenticationMiddleware.cs#L35 which uses the prefix defined at https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.Authentication.Cookies/CookieAuthenticationDefaults.cs#L22

edit: Oops seems like I forgot to write that in the issue, sorry about that.

[natemcmaster]

So to be clear, the expected cookie name is Identity.Application or Identity.External? there is no "Microsoft" or "AspNetCore" anymore?

[JunTaoLuo]

No, it is expected to be .AspNetCore.Identity.Application it's just that the .AspNetCore. part is added by Cookies Middleware already.

[natemcmaster]

Ok. LGTM

[JunTaoLuo]

ping @HaoK

[HaoK]