[Week view] personal notes only work when filtering by group

When aggregating personal notes, use the participants of the selected lesson periods.

changed milestone to %1.0a2

added part::backend type::bug labels

mentioned in commit c5ee866a

changed milestone to %1.0a3

changed the description

removed milestone

assigned to @debdolph and unassigned @nik

changed milestone to %1.0a3

created merge request !30 (merged) to address this issue

mentioned in merge request !30 (merged)

closed via merge request !30 (merged)

mentioned in commit 3e2b537b