feat: Add a view for mentions (#3505)

- Added a new table mentions for saving user mentions
- Added a filter conversation_type in the API
- Added a view to see the mentions

app/finders/conversation_finder.rb

@@ -70,7 +70,12 @@ class ConversationFinder
   end
 
   def find_all_conversations
-    @conversations = current_account.conversations.where(inbox_id: @inbox_ids)
+    if params[:conversation_type] == 'mention'
+      conversation_ids = current_account.mentions.where(user: current_user).pluck(:conversation_id)
+      @conversations = current_account.conversations.where(id: conversation_ids)
+    else
+      @conversations = current_account.conversations.where(inbox_id: @inbox_ids)
+    end
   end
 
   def filter_by_assignee_type
@@ -123,6 +128,10 @@ class ConversationFinder
     @conversations = @conversations.includes(
       :taggings, :inbox, { assignee: { avatar_attachment: [:blob] } }, { contact: { avatar_attachment: [:blob] } }, :team, :contact_inbox
     )
-    @conversations.latest.page(current_page)
+    if params[:conversation_type] == 'mention'
+      @conversations.page(current_page)
+    else
+      @conversations.latest.page(current_page)
+    end
   end
 end