settings: Add group_permission_settings.ts.

This commit adds a new module group_permission_settings.ts
which is used to define configuration options like
allow_owners_group, allow_nobody_group, etc. for group-based
settings similar to GroupPermissionSetting dataclass we have
in backend.

tools/test-js-with-node

@@ -91,6 +91,7 @@ EXEMPT_FILES = make_set(
         "web/src/gear_menu.ts",
         "web/src/giphy.js",
         "web/src/global.d.ts",
+        "web/src/group_permission_settings.ts",
         "web/src/hash_util.js",
         "web/src/hashchange.js",
         "web/src/hbs.d.ts",

web/src/group_permission_settings.ts

@@ -0,0 +1,28 @@
+type GroupPermissionSetting = {
+    require_system_group: boolean;
+    allow_internet_group: boolean;
+    allow_owners_group: boolean;
+    allow_nobody_group: boolean;
+};
+
+const group_permission_config_dict: Map<string, GroupPermissionSetting> = new Map([
+    [
+        "can_remove_subscribers_group",
+        {
+            require_system_group: true,
+            allow_internet_group: false,
+            allow_owners_group: false,
+            allow_nobody_group: false,
+        },
+    ],
+]);
+
+export function get_group_permission_setting_config(
+    setting_name: string,
+): GroupPermissionSetting | undefined {
+    const permission_config_dict = group_permission_config_dict.get(setting_name);
+    if (!permission_config_dict) {
+        throw new Error(`Invalid setting: ${setting_name}`);
+    }
+    return permission_config_dict;
+}