api.content.create lacks schema validation

As seen in https://community.plone.org/t/creating-custom-dexterity-objects-from-plone-api/7318/ we can currently set an invalid value/type for fields.
In this case the user is setting a str instead of a RichTextValue, which leads to tracebacks like

AttributeError: 'str' object has no attribute 'output_relative_to'

 - Expression: "python:context.text.output_relative_to(view.context)"
 - Filename:   ... egg/plone/app/contenttypes/browser/templates/document.pt
 - Location:   (line 15: col 29)
 - Source:     ... ucture python:context.text.output_relative_to(view.context)"
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Is this something we need to handle here, or is this something DX should do?

Start at the api.content.create entry point and review the linked community discussion about invalid field values. Reproduce the case where a string is supplied instead of a RichTextValue, then determine whether validation belongs in this API or in Dexterity. Done means invalid values are handled with a clear validation error rather than a later template traceback.