cubicweb #5271058 [mail] include Date header in generated mails [validation pending]

[mail] include Date header in generated mails

prioritynormal
typebug
done in3.20.7
load0.500
load left0.000
closed by#03d98646d57c [mail] include Date header in generated mails (closes #5271058)
patch[mail] include Date header in generated mails (closes #5271058) [applied]