Frontend for additional fields for group

Provide a frontend for creating additional field and connect them to groups

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

assigned to @debdolph

created merge request !271 (merged) to address this issue

mentioned in merge request !271 (merged)

closed via merge request !271 (merged)

mentioned in commit 3c6a0e42

mentioned in merge request !300 (merged)

mentioned in commit d118bb96

mentioned in merge request Teckids/ticdesk!55