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/models/conversation.rb

@@ -71,6 +71,7 @@ class Conversation < ApplicationRecord
   belongs_to :team, optional: true
   belongs_to :campaign, optional: true
 
+  has_many :mentions, dependent: :destroy_async
   has_many :messages, dependent: :destroy_async, autosave: true
   has_one :csat_survey_response, dependent: :destroy_async
   has_many :notifications, as: :primary_actor, dependent: :destroy