For the mail app we had to build a form without the so called dialog chrome, which you see for example in the contant app detail views.
We have put some effort into separating the Dialog look and feel from the actual form inside it, but haven't pushed it far enough. This change is driving the separation one step further in the right direction, so you actually can populate the form with the fields from definition without adding the chrome. This could be driven further, but I suggest doing a clean up including renaming interfaces and methods in 5.2.

While this is not 100% api compatible, the only change that is breaking is changing the info.magnolia.ui.vaadin.form.FormViewReduced#asVaadinComponent() to return Component instead of Form. See attached clirr report.