feat: Add APIs for Campaigns (#2175)

app/policies/campaign_policy.rb

@@ -0,0 +1,21 @@
+class CampaignPolicy < ApplicationPolicy
+  def index?
+    @account_user.administrator?
+  end
+
+  def update?
+    @account_user.administrator?
+  end
+
+  def show?
+    @account_user.administrator?
+  end
+
+  def create?
+    @account_user.administrator?
+  end
+
+  def destroy?
+    @account_user.administrator?
+  end
+end