FEATURE: Enforce mention limits for chat messages (#19034)

* FEATURE: Enforce mention limits for chat messages

The first part of these changes adds a new setting called `max_mentions_per_chat_message`, which skips notifications when the message contains too many mentions. It also respects the `max_users_notified_per_group_mention` setting
and skips notifications if expanding a group mention would exceed it.

We also include a new component to display JIT warning for these limits to the user while composing a message.

* Simplify ignoring/muting filter in chat_notifier

* Post-send warnings for unsent warnings

* Improve pluralization

* Address review feedback

* Fix test

* Address second feedback round

* Third round of feedback

Co-authored-by: Joffrey JAFFEUX <j.jaffeux@gmail.com>

plugins/chat/test/javascripts/acceptance/chat-composer-test.js

@@ -17,6 +17,8 @@ import {
   chatChannelPretender,
 } from "../helpers/chat-pretenders";
 
+const GROUP_NAME = "group1";
+
 acceptance("Discourse Chat - Composer", function (needs) {
   needs.user({ has_chat_enabled: true });
   needs.settings({ chat_enabled: true, enable_rich_text_paste: true });
@@ -32,6 +34,14 @@ acceptance("Discourse Chat - Composer", function (needs) {
     server.post("/chat/drafts", () => {
       return helper.response([]);
     });
+
+    server.get("/chat/api/mentions/groups.json", () => {
+      return helper.response({
+        unreachable: [GROUP_NAME],
+        over_members_limit: [],
+        invalid: [],
+      });
+    });
   });
 
   needs.hooks.beforeEach(function () {
@@ -105,6 +115,18 @@ acceptance("Discourse Chat - Composer", function (needs) {
       "it tracks the emoji"
     );
   });
+
+  test("JIT warnings for group mentions", async function (assert) {
+    await visit("/chat/channel/11/-");
+    await fillIn(".chat-composer-input", `@${GROUP_NAME}`);
+
+    assert.equal(
+      query(".chat-mention-warnings .chat-mention-warnings-list__simple li")
+        .innerText,
+      `@${GROUP_NAME} doesn't allow mentions`,
+      "displays a warning when the group is unreachable"
+    );
+  });
 });
 
 let sendAttempt = 0;

plugins/chat/test/javascripts/acceptance/chat-test.js

@@ -864,7 +864,7 @@ Widget.triangulate(arg: "test")
       ".chat-message-container[data-id='176'] .chat-message-mention-warning .without-membership"
     ).innerText;
     assert.ok(withoutMembershipText.includes("eviltrout"));
-    assert.ok(withoutMembershipText.includes("sam"));
+    assert.ok(withoutMembershipText.includes("1 other"));
 
     await click(
       ".chat-message-container[data-id='176'] .chat-message-mention-warning .invite-link"