def fixed_attributes
      if model_class
        presence_validators = model_class.validators.detect { |x| x.kind_of?(ActiveRecord::Validations::PresenceValidator) }
      end
      # Attributes that has to be always on the entity, so attributes making unique index of the record + attributes
      # that have presence validation
      fixed_attributes = manager_ref
      fixed_attributes += presence_validators.attributes if presence_validators.present?
      fixed_attributes
    end
def fixed_attributes
      if model_class
        presence_validators = model_class.validators.detect { |x| x.kind_of?(ActiveRecord::Validations::PresenceValidator) }
      end
      # Attributes that has to be always on the entity, so attributes making unique index of the record + attributes
      # that have presence validation
      fixed_attributes = manager_ref
      fixed_attributes += presence_validators.attributes if presence_validators.present?
      fixed_attributes
    end
Attributes that are needed to be able to save the record, i.e. attributes that are part of the unique index
 and attributes with presence validation or NOT NULL constraint

 @return [Array<Symbol>] attributes that are needed for saving of the record