Add a JS file for use with SelectColumn

aleksis/core/static/js/multi_select.js

+$(document).ready(function () {
+    $("#select_all_container").show();
+    $("#header_box").change(function () {
+        if ($(this).is(":checked")) {
+            $(document).find('input[name="selected_objects"]').prop({
+                indeterminate: false,
+                checked: true,
+            });
+        } else {
+            $(document).find('input[name="selected_objects"]').prop({
+                indeterminate: false,
+                checked: false,
+            });
+        }
+    });
+
+    $('input[name="selected_objects"]').change(function () {
+        let checked = $(this).is(":checked");
+        let indeterminate = false;
+        $(document).find('input[name="selected_objects"]').each(function () {
+            if ($(this).is(":checked") !== checked) {
+                $("#header_box").prop({
+                    indeterminate: true,
+                })
+                indeterminate = true;
+                return false;
+            }
+        });
+        if (!(indeterminate)) {
+            $("#header_box").prop({
+                indeterminate: false,
+                checked: checked,
+            });
+        }
+    });
+});