settings: Add moderators option for wildcard_mention_policy in frontend.

frontend_tests/node_tests/compose.js

@@ -367,6 +367,14 @@ test_ui("test_wildcard_mention_allowed", () => {
     page_params.is_guest = false;
     assert(compose.wildcard_mention_allowed());
 
+    page_params.realm_wildcard_mention_policy =
+        settings_config.wildcard_mention_policy_values.by_moderators_only.code;
+    page_params.is_moderator = false;
+    assert(!compose.wildcard_mention_allowed());
+
+    page_params.is_moderator = true;
+    assert(compose.wildcard_mention_allowed());
+
     page_params.realm_wildcard_mention_policy =
         settings_config.wildcard_mention_policy_values.by_stream_admins_only.code;
     page_params.is_admin = false;

static/js/compose.js

@@ -522,6 +522,13 @@ export function wildcard_mention_allowed() {
         // TODO: Check the user's stream-level role once stream-level admins exist.
         return page_params.is_admin;
     }
+
+    if (
+        page_params.realm_wildcard_mention_policy ===
+        settings_config.wildcard_mention_policy_values.by_moderators_only.code
+    ) {
+        return page_params.is_admin || page_params.is_moderator;
+    }
     // TODO: Uncomment when we add support for stream-level administrators.
     // if (
     //     page_params.realm_wildcard_mention_policy ===

static/js/settings_config.js

@@ -168,11 +168,16 @@ export const wildcard_mention_policy_values = {
         code: 3,
         description: $t({defaultMessage: "Admins and full members"}),
     },
+    by_moderators_only: {
+        order: 4,
+        code: 7,
+        description: $t({defaultMessage: "Admins and moderators"}),
+    },
     // Until we add stream administrators, we mislabel this choice
     // (which we intend to be the long-term default) as "Admins only"
     // and don't offer the long-term "Admins only" option.
     by_stream_admins_only: {
-        order: 4,
+        order: 5,
         code: 4,
         //  description: $t({defaultMessage: "Organization and stream admins"}),
         description: $t({defaultMessage: "Admins only"}),