User impersonation

Enable user impersonation to ease support.

changed due date to September 02, 2019

changed milestone to %1.0a1

added part::backend prio::1 type::feature labels

removed due date

mentioned in commit 0c85fdad

mentioned in commit b8ad8a12

closed via commit 8faee50c

mentioned in commit 4a69fd29

changed milestone to %2.0a2

added part::backend part::frontend prio::2 type::feature workflow::confirmed labels