Improve code coverage for app/models/user.rb

Related to Improve code coverage for app/models/user.rb (#435160 - closed) which added coverage to app/models/user.rb relating to [Source Code Backend] FCL for Incident 17213 (gitlab-com&2265 - closed).

This Issue tracks adding coverage to the remaining code that was unrelated.

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Fix the test gaps reported for this file on https://gitlab-org.gitlab.io/gitlab/coverage-ruby/

As of 00769538, the current coverage gaps for User (https://gitlab-org.gitlab.io/gitlab/coverage-ruby/#35c38ceff63c512a6a8b1f4d336518a9b805040d) are:

From line 712:

+    def find_for_database_authentication(warden_conditions)
+       conditions = warden_conditions.dup
+       if login = conditions.delete(:login)
+         where(conditions).find_by("lower(username) = :value OR lower(email) = :value", value: login.downcase.strip)
      else
-        find_by(conditions)
      end
    end

From line 767:

+   def filter_items(filter_name)
+     case filter_name
      when 'admins'
+        admins
      when 'blocked'
+        blocked
      when 'blocked_pending_approval'
+        blocked_pending_approval
      when 'banned'
+        banned
      when 'two_factor_disabled'
+        without_two_factor
      when 'two_factor_enabled'
+        with_two_factor
      when 'wop'
+        without_projects
      when 'external'
-       external
      when 'deactivated'
+        deactivated
      when "trusted"
+        trusted
      else
+        active_without_ghosts
      end
    end

From line 1383:

def crowd_user?
+  if identities.loaded?
-    identities.find { |identity| identity.provider == 'crowd' && identity.extern_uid.present? }
  else
+    identities.with_any_extern_uid('crowd').exists?
  end
end

From line 1475:

+ def ldap_sync_time
   # This number resides in this method so it can be redefined in EE.
-  1.hour
end

From line 1508:

+  def can_leave_project?(project)
-    project.namespace != namespace &&
      project.member(self)
  end

From line 1812:

+  def can_remove_self?
-    true
  end

From line 1981:

+  def access_level=(new_level)
-    new_level = new_level.to_s
-    return unless %w[admin regular].include?(new_level)

-     self.admin = (new_level == 'admin')
  end

From line 2304:

+  def consume_otp!
+    if self.consumed_timestep != current_otp_timestep
+      self.consumed_timestep = current_otp_timestep
+      return Gitlab::Database.read_only? ? true : save(validate: false)
    end

-     false
  end

From line 2426:

+  def has_current_license?
-    false
  end