cubicweb-massmailing #4457903 extract massmailing from cw (<3.17) [validation pending]

prioritynormal
typebug
done in0.1.0
load1.000
load left0.000
closed by#107e09797f09 Initial creation of cube (closes #4457903)
patchdrop useless files, rename test module to reflect it is not automatic tests (related to #4457903) [applied]Initial creation of cube (closes #4457903) [applied]