cubicweb-preview #3216719 Improve API for forms to force iframe for posting [resolved]

This form post method is mandatory with current way to handle the preview display: setting it in the preview form mixin would make it easier to use the preview cube with forms that are not AutomaticEntityForm instances (that use iframe form posting anyway).

done in1.1.0
load left0.000
closed by#6540ec56e679 Force usage of iframe form posting.
patchForce usage of iframe form posting. [applied]