public FormBuilder::doBuildForm($form_id, &$element, FormStateInterface &$form_state)
Builds and processes all elements in the structured form array.
Adds any required properties to each element, maps the incoming input data to the proper elements, and executes any #process handlers attached to a specific element.
This is one of the three primary functions that recursively iterates a form array. This one does it for completing the form building process. The other two are self::doValidat