do not display links to groups in WP table
test assigned_to field rendering in WP table
remove superfluous comment
don't die when the assigned_to field is not set on a WP
add subtype to principals in apiv2

so we can differentiate between the different types of principals
(users vs. groups)
do not render a link to a group-assigned in a related work package
in WP details view do not link to groups
Merge pull request #1994 from opf/fix/15661_no_link_to_groups

Fix #15661: no link to groups