feat: sla-7 ensure applied_sla uniqueness (#8938)

* feat: refactor fetching sla in action service

* chore: modify spec

* chore: ensure applied_sla uniqueness

* chore: review fixes

* feat: add unique index on applied_sla

* chore: fix spec

* chore: add new specs to improve coverage

* chore: improve spec

* Update spec/enterprise/services/enterprise/action_service_spec.rb

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

enterprise/app/services/enterprise/action_service.rb

@@ -1,10 +1,18 @@
 module Enterprise::ActionService
-  def add_sla(sla_policy)
+  def add_sla(sla_policy_id)
+    return if sla_policy_id.blank?
+
+    sla_policy = @account.sla_policies.find_by(id: sla_policy_id.first)
+    return if sla_policy.nil?
+    return if @conversation.sla_policy.present?
+
+    Rails.logger.info "SLA:: Adding SLA #{sla_policy.id} to conversation: #{@conversation.id}"
     @conversation.update!(sla_policy_id: sla_policy.id)
     create_applied_sla(sla_policy)
   end
 
   def create_applied_sla(sla_policy)
+    Rails.logger.info "SLA:: Creating Applied SLA for conversation: #{@conversation.id}"
     AppliedSla.create!(
       account_id: @conversation.account_id,
       sla_policy_id: sla_policy.id,