Drupal attribute properties break form generator

Problem/Motivation

In the SDC documentation, it is mentioned that SDC properties can include Drupal attributes → . However, in practice this breaks the SDC Display with a white screen reading "FormGeneratorDrupal received invalid input data".

Steps to reproduce

Create a component with an attributes property:

  attributes:
    type: Drupal\Core\Template\Attribute

Then try to use it in manage display with SDC display.

Proposed resolution

• Update the schema validation to allow Drupal Attribute objects.
• Update the SDC display form so users can specify HTML attributes for an Attribute property.