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/jobs/conversations/user_mention_job.rb

@@ -0,0 +1,24 @@
+class Conversations::UserMentionJob < ApplicationJob
+  queue_as :default
+
+  def perform(mentioned_user_ids, conversation_id, account_id)
+    mentioned_user_ids.each do |mentioned_user_id|
+      mention = Mention.find_by(
+        user_id: mentioned_user_id,
+        conversation_id: conversation_id,
+        account_id: account_id
+      )
+
+      if mention.nil?
+        Mention.create(
+          user_id: mentioned_user_id,
+          conversation_id: conversation_id,
+          mentioned_at: Time.zone.now,
+          account_id: account_id
+        )
+      else
+        mention.update(mentioned_at: Time.zone.now)
+      end
+    end
+  end
+end