feat: add unified IM access policies

test/channels/access-policy-fixture.mjs

@@ -0,0 +1,35 @@
+export { COMMAND_PERMISSION_DENIED_MESSAGE } from '../../src/channels/shared/inbound-access.mjs';
+
+function scope(users = []) {
+  return {
+    mode: 'allowlist',
+    open: {
+      defaultCanExecuteCommands: false,
+      commandPermissionOverrides: [],
+    },
+    allowlist: {
+      users: users.map(({ id, canExecuteCommands = false }) => ({
+        id,
+        canExecuteCommands,
+      })),
+    },
+  };
+}
+
+export function directAccessPolicy({
+  users = [],
+  privilegedIds = [],
+} = {}) {
+  const privileged = new Set(privilegedIds);
+  const settings = {
+    direct: scope(users),
+    group: scope(),
+  };
+  return {
+    getSettings: () => settings,
+    isPrivileged: (senderIds) => (
+      (Array.isArray(senderIds) ? senderIds : [senderIds])
+        .some((senderId) => privileged.has(senderId))
+    ),
+  };
+}