Refine user uniqueness validation logic

Author: maliming

modules/identity/src/Volo.Abp.Identity.Domain/Volo/Abp/Identity/AbpIdentityUserValidator.cs

@@ -109,18 +109,27 @@ protected virtual async Task<IdentityResult> ValidateSharedUserAsync(UserManager
             {
                 using (TenantFilter.Disable())
                 {
+                    var owner = await manager.FindByIdAsync(user.Id.ToString());
                     var normalizedUserName = manager.NormalizeName(user.UserName);
                     var normalizedEmail = manager.NormalizeEmail(user.Email);
                     var users = await UserRepository.GetUsersByNormalizedUserNamesAsync([normalizedUserName!, normalizedEmail], true);
-                    users.RemoveAll(x => x.Id == user.Id || x.NormalizedUserName == user.NormalizedUserName || x.NormalizedEmail == user.NormalizedEmail);
+                    users.RemoveAll(x => x.Id == user.Id);
+                    if (owner != null)
+                    {
+                        users.RemoveAll(x => x.NormalizedUserName == user.NormalizedUserName || x.NormalizedEmail == user.NormalizedEmail);
+                    }
                     if (users.Any())
                     {
                         var userNames = users.Select(u => u.UserName).ToList();
                         errors.Add(userNames.Contains(user.UserName) ? ErrorDescriber.DuplicateUserName(user.UserName!) : ErrorDescriber.DuplicateEmail(user.Email!));
                     }
 
                     users = await UserRepository.GetUsersByNormalizedEmailsAsync([normalizedUserName!, normalizedEmail], true);
-                    users.RemoveAll(x => x.Id == user.Id || x.NormalizedUserName == user.NormalizedUserName || x.NormalizedEmail == user.NormalizedEmail);
+                    users.RemoveAll(x => x.Id == user.Id);
+                    if (owner != null)
+                    {
+                        users.RemoveAll(x => x.NormalizedUserName == user.NormalizedUserName || x.NormalizedEmail == user.NormalizedEmail);
+                    }
                     if (users.Any())
                     {
                         var emails = users.Select(u => u.Email).ToList();