DEV: /channel -> /c chat route rename (#19782)

* DEV: Rnemae channel path to just c

Also swap the channel id and channel slug params to be consistent with core.

* linting

* channel_path

* params in wrong order

* Drop slugify helper and channel route without slug

* Request slug and route models through the channel model if possible

* Add client side redirection for backwards-compatibility

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

plugins/chat/assets/javascripts/discourse/widgets/chat-invitation-notification-item.js

@@ -38,7 +38,7 @@ createWidgetFrom(DefaultNotificationItem, "chat-invitation-notification-item", {
       title: data.chat_channel_title,
       slug: data.chat_channel_slug,
     });
-    return `/chat/channel/${data.chat_channel_id}/${slug || "-"}?messageId=${
+    return `/chat/c/${slug || "-"}/${data.chat_channel_id}?messageId=${
       data.chat_message_id
     }`;
   },

plugins/chat/assets/javascripts/discourse/widgets/chat-mention-notification-item.js

@@ -48,7 +48,7 @@ const chatNotificationItem = {
       title: data.chat_channel_title,
       slug: data.chat_channel_slug,
     });
-    return `/chat/channel/${data.chat_channel_id}/${slug || "-"}?messageId=${
+    return `/chat/c/${slug || "-"}/${data.chat_channel_id}?messageId=${
       data.chat_message_id
     }`;
   },