feat: Add push/email notification support for SLA (#9140)

* feat: update SLA evaluation logic

* Update enterprise/app/services/sla/evaluate_applied_sla_service.rb

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

* chore: refactor spec to bring down expecations in a single block

* chore: fix process_account_applied_sla spec

* chore: add spec to test multiple nrt misses

* feat: persist sla notifications

* feat: revert persist sla notifications

* feat: add SLA push/email notification support

* chore: refactor sla_status to include active_with_misses

* chore: add support for sla push/email notifications

* chore: refactor

* chore: add liquid templates

* chore: add spec for liquid templates

* chore: add spec for sla email notifications

* chore: add spec for SlaPolicyDrop

* chore: refactor to ee namespace

* chore: set enterprise test type to mailer

* feat: enable sla notification settings only if SLA enabled

* chore: refactor

* chore: fix spec

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/models/application_record.rb

@@ -5,11 +5,13 @@ class ApplicationRecord < ActiveRecord::Base
   before_validation :validates_column_content_length
 
   # the models that exposed in email templates through liquid
-  DROPPABLES = %w[Account Channel Conversation Inbox User Message].freeze
+  def droppables
+    %w[Account Channel Conversation Inbox User Message]
+  end
 
   # ModelDrop class should exist in app/drops
   def to_drop
-    return unless DROPPABLES.include?(self.class.name)
+    return unless droppables.include?(self.class.name)
 
     "#{self.class.name}Drop".constantize.new(self)
   end
@@ -47,3 +49,5 @@ class ApplicationRecord < ActiveRecord::Base
     end
   end
 end
+
+ApplicationRecord.include_mod_with('Enterprise::ApplicationRecord')