Add record to track overridden limits

Before, we were relying on just changing the cards_count in account, but this
could create problems where the system to calculate the next card number fails due
to the unique constraint.

saas/app/models/account/billing.rb

@@ -5,8 +5,6 @@ module Account::Billing
     has_one :subscription, class_name: "Account::Subscription", dependent: :destroy
   end
 
-  NEAR_CARD_LIMIT_THRESHOLD = 100
-
   def plan
     active_subscription&.plan || Plan.free
   end
@@ -18,12 +16,4 @@ module Account::Billing
   def subscribed?
     subscription.present?
   end
-
-  def nearing_plan_cards_limit?
-    plan.limit_cards? && (plan.card_limit - cards_count) < NEAR_CARD_LIMIT_THRESHOLD
-  end
-
-  def exceeding_card_limit?
-    cards_count > plan.card_limit
-  end
 end

saas/app/models/account/limited.rb

@@ -0,0 +1,34 @@
+module Account::Limited
+  extend ActiveSupport::Concern
+
+  included do
+    has_one :overridden_limits, class_name: "Account::OverriddenLimits", dependent: :destroy
+  end
+
+  NEAR_CARD_LIMIT_THRESHOLD = 100
+
+  def override_limits(card_count:)
+    if overridden_limits
+      overridden_limits.update(card_count: card_count)
+    else
+      create_overridden_limits(card_count: card_count)
+    end
+  end
+
+  def billed_cards_count
+    overridden_limits&.card_count || cards_count
+  end
+
+  def nearing_plan_cards_limit?
+    plan.limit_cards? && (plan.card_limit - billed_cards_count) < NEAR_CARD_LIMIT_THRESHOLD
+  end
+
+  def exceeding_card_limit?
+    plan.limit_cards? && billed_cards_count > plan.card_limit
+  end
+
+  def reset_overridden_limits
+    overridden_limits&.destroy
+    reload_overridden_limits
+  end
+end

saas/app/models/account/overridden_limits.rb

@@ -0,0 +1,4 @@
+# To ease testing of limits
+class Account::OverriddenLimits < SaasRecord
+  belongs_to :account
+end