🐛 Incoherent cache results #304

Bug Description

In a multi-user application, I have a select2 field (overriding widget queryset according to the user, see code below) which retrieve data according to the workspace of the current authenticated user, but a user can switch workspace at will through a menu and "sometimes" the select2 list displays results from the previous workspace, and "rarely" it even displays results from other users' workspaces, which is problematic. It looks like a cache issue to me.

In my modest opinion, a solution could be to have the ability to add a cache prefix key per user or configurable directly on the widget and/or the form.

class LinkForm(ModelForm):
    tags = forms.ModelMultipleChoiceField(
        required=False,
        label=_("Tags"),
        queryset=Tag.objects.order_by("order", "name"),
        widget=ModelSelect2MultipleWidget(
            queryset=Tag.objects.order_by("order", "name"),
            search_fields=("code__icontains", "name__icontains"),
            attrs={"data-minimum-input-length": 0},
        ),
    )

    def __init__(self, *args, request=None, **kwargs):
        self.request = request
        super().__init__(*args, **kwargs)
        if self.request:
            field = self.fields["tags"]
            workspace = self.request.session.get("current_workspace")
            if workspace:
                field.queryset = field.queryset.filter(workspace_id=workspace)
            else:
                field.queryset = field.queryset.none()
            field.widget.queryset = field.queryset

    class Meta:
        model = Link
        fields = (
            "tags",
        )

Steps to Reproduce

1. User A, using Workspace 1, see list items from Workspace 1.
2. User A, switch to Workspace 2, see list items from Workspace 2.
3. User A, switch to Workspace 1 again, see list items from Workspace 2 (?).

?) User B, using Workspace 9, see list items from Workpace 1 which belongs to User A.

Expected Behavior

I expect the results from select2 droplists to be coherent with the queryset.