add an option for group multiselect to require entries to be in all selected groups (AND instead of OR condition)

[wschlich]

currently, an entry can be a member of multiple groups.

when the behaviour option "multiselect groups" is activated, multiple groups can be selected at once in the entry list which effectively ORs the group membership condition, thus showing entries which are members of any of the selected groups.

while this is probably useful at times, it would (IMHO) be much more useful to have the group membership condition ANDed and thus only showing entries which are members of all of the selected groups.

this would allow more powerful entry list filtering.

it might be a good idea to make the condition (AND, OR) configurable for the "multiselect groups" behaviour option.

Thank you! 😃