cubicweb-relationwidget #10184674 Add unittests for the server-side behaviour [validation pending]

This is a bare minimum before going to production:

  • trigger buttons presence
  • creation tab presence
  • new pagination behaviours
  • uicfg customizations
prioritynormal
typeenhancement
done in0.3.3
load0.500
load left0.000
closed by#063b56d8e9a5 [tests] Add python tests
patch[tests] Small refactoring [applied][tests] Add python tests [applied]