Add argument to lesson events get_objects method that bypasses the filtering done if own=False

changed milestone to /AlekSIS%"[NLnet #6 (closed)] Fix bugs/missing small features from pilot schools"

added part::backend label

assigned to @yuha

created branch 281-add-argument-to-lesson-events-get_objects-method-that-bypasses-the-filtering-done-if-own-false to address this issue

mentioned in merge request !412