refactor(core): move identity models from API to Core

src/FiscalOS.Core/Identity/RefreshToken.cs

@@ -0,0 +1,7 @@
+namespace FiscalOS.Core.Identity;
+
+public sealed class RefreshToken : Entity
+{
+  public Guid UserId { get; init; }
+  public User User { get; init; } = new();
+}