cubicweb #2262340 need a proper way to check if a form is being generated or posted [validation pending]

since 3.13(?), form are also used by controllers to do proper values retreiving / validation. So a need for custom code is to check if the form is being generated or posted.

prioritynormal
typeenhancement
done in3.14.7
load0.100
load left0.000
closed by#b5275e739a44 [form] add a new property telling if the form is being generated or posted. Closes #2262340