update seed generator and remove hard-coded customer id

app/controllers/concerns/customers.rb

@@ -0,0 +1,18 @@
+module Customers
+  extend ActiveSupport::Concern
+
+  included do
+    helper_method :walkin, :takeaway if respond_to? :helper_method
+  end
+
+  def walkin
+    return @walkin if defined? @walkin
+    @walkin = Customer.walkin
+  end
+
+  def takeaway
+    return @takeaway if defined? @takeaway
+    @takeaway = Customer.takeaway
+  end
+
+end