feat: Conversation update API for sla_policy_id (#8973)

- Add an endpoint for updating conversation attributes (priority / sla_policy_id )
- Swagger spec
- minor chores around the conversation API/spec

Fixes: https://linear.app/chatwoot/issue/CW-2100/feat-backend-api-to-update-the-sla-of-a-conversation

spec/enterprise/services/sla/evaluate_applied_sla_service_spec.rb

@@ -5,14 +5,21 @@ RSpec.describe Sla::EvaluateAppliedSlaService do
   let!(:user_1) { create(:user, account: account) }
   let!(:user_2) { create(:user, account: account) }
   let!(:admin) { create(:user, account: account, role: :administrator) }
-  let!(:conversation) { create(:conversation, created_at: 6.hours.ago, assignee: user_1, account: account) }
+
   let!(:sla_policy) do
-    create(:sla_policy, account: conversation.account,
-                        first_response_time_threshold: nil,
-                        next_response_time_threshold: nil,
-                        resolution_time_threshold: nil)
+    create(:sla_policy,
+           account: account,
+           first_response_time_threshold: nil,
+           next_response_time_threshold: nil,
+           resolution_time_threshold: nil)
   end
-  let!(:applied_sla) { create(:applied_sla, conversation: conversation, sla_policy: sla_policy, sla_status: 'active') }
+  let!(:conversation) do
+    create(:conversation,
+           created_at: 6.hours.ago, assignee: user_1,
+           account: sla_policy.account,
+           sla_policy: sla_policy)
+  end
+  let!(:applied_sla) { conversation.applied_sla }
 
   describe '#perform - SLA misses' do
     context 'when first response SLA is missed' do