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/team_activity_message_handler.rb

@@ -0,0 +1,29 @@
+module TeamActivityMessageHandler
+  extend ActiveSupport::Concern
+
+  private
+
+  def create_team_change_activity(user_name)
+    user_name = activity_message_owner(user_name)
+    return unless user_name
+
+    key = generate_team_change_activity_key
+    params = { assignee_name: assignee&.name, team_name: team&.name, user_name: user_name }
+    params[:team_name] = generate_team_name_for_activity if key == 'removed'
+    content = I18n.t("conversations.activity.team.#{key}", **params)
+
+    ::Conversations::ActivityMessageJob.perform_later(self, activity_message_params(content)) if content
+  end
+
+  def generate_team_change_activity_key
+    team = Team.find_by(id: team_id)
+    key = team.present? ? 'assigned' : 'removed'
+    key += '_with_assignee' if key == 'assigned' && saved_change_to_assignee_id? && assignee
+    key
+  end
+
+  def generate_team_name_for_activity
+    previous_team_id = previous_changes[:team_id][0]
+    Team.find_by(id: previous_team_id)&.name if previous_team_id.present?
+  end
+end