add specs

app/models/group_order_invoice.rb

@@ -1,34 +1,9 @@
 class GroupOrderInvoice < ApplicationRecord
-  include InvoiceHelper
+  include InvoiceCommon
 
   belongs_to :group_order
   validates_presence_of :group_order
-  validates_uniqueness_of :invoice_number
-  validate :tax_number_set
-  after_initialize :init, unless: :persisted?
-
-  enum sequence_type: {
-    FRST: "Erst-Lastschrift",
-    RCUR: "Folge-Lastschrift",
-    OOFF: "Einmalige Lastschrift",
-    FNAL: "Letztmalige Lastschrift"
-  }
-
-  def tax_number_set
-    return unless FoodsoftConfig[:contact][:tax_number].blank?
-
-    errors.add(:group_order_invoice, "Keine Steuernummer in FoodsoftConfig :contact gesetzt")
-  end
-
-  def mark_sepa_downloaded
-    self.sepa_downloaded = true
-    self.save
-  end
-
-  def unmark_sepa_downloaded
-    self.sepa_downloaded = false
-    self.save
-  end
+  validates_uniqueness_of :group_order_id
 
   def init
     self.invoice_date = Time.now unless invoice_date
@@ -36,10 +11,6 @@ class GroupOrderInvoice < ApplicationRecord
     self.payment_method = group_order&.financial_transaction&.financial_transaction_type&.name || FoodsoftConfig[:group_order_invoices]&.[](:payment_method) || I18n.t('activerecord.attributes.group_order_invoice.payment_method') unless self.payment_method
   end
 
-  def name
-    I18n.t('activerecord.attributes.group_order_invoice.name') + "_#{invoice_number}"
-  end
-
   def load_data_for_invoice
     invoice_data = {}
     order = group_order.order