feat: add activity message for SLA (#9100)

* feat: add activity message for SLA

* chore: refactor to reduce method complexity

* chore: refactor

* feat: add spec for SLAactivity message

* chore: move SLA spec to enterprise folder

* chore: move team activity methods to a separate module

* chore: fix typo

* chore: move sla activity message spec to conversation model

app/models/concerns/label_activity_message_handler.rb

@@ -0,0 +1,20 @@
+module LabelActivityMessageHandler
+  extend ActiveSupport::Concern
+
+  private
+
+  def create_label_added(user_name, labels = [])
+    create_label_change_activity('added', user_name, labels)
+  end
+
+  def create_label_removed(user_name, labels = [])
+    create_label_change_activity('removed', user_name, labels)
+  end
+
+  def create_label_change_activity(change_type, user_name, labels = [])
+    return unless labels.size.positive?
+
+    content = I18n.t("conversations.activity.labels.#{change_type}", user_name: user_name, labels: labels.join(', '))
+    ::Conversations::ActivityMessageJob.perform_later(self, activity_message_params(content)) if content
+  end
+end