compose: Add banner for unmuting the muted topic a message is sent to.

We add a new banner informing the user if and when they send a message
to a muted topic / stream. It also has a button to unmute the topic.

Fixes: #24246.

web/src/compose.js

@@ -39,6 +39,7 @@ import * as transmit from "./transmit";
 import * as ui_report from "./ui_report";
 import * as upload from "./upload";
 import {user_settings} from "./user_settings";
+import * as user_topics from "./user_topics";
 import * as util from "./util";
 import * as zcommand from "./zcommand";
 
@@ -515,6 +516,28 @@ export function initialize() {
         },
     );
 
+    $("#compose_banners").on(
+        "click",
+        `.${CSS.escape(
+            compose_banner.CLASSNAMES.unmute_topic_notification,
+        )} .compose_banner_action_button`,
+        (event) => {
+            event.preventDefault();
+
+            const $target = $(event.target).parents(".compose_banner");
+            const stream_id = Number.parseInt($target.attr("data-stream-id"), 10);
+            const topic_name = $target.attr("data-topic-name");
+
+            user_topics.set_user_topic_visibility_policy(
+                stream_id,
+                topic_name,
+                user_topics.all_visibility_policies.UNMUTED,
+                false,
+                true,
+            );
+        },
+    );
+
     $("#compose_banners").on(
         "click",
         `.${CSS.escape(