Remove unused attribute

#772

app/models/directo.rb

@@ -3,7 +3,7 @@ class Directo < ActiveRecord::Base
   belongs_to :item, polymorphic: true
 
   def self.send_receipts
-    new_trans = Invoice.where(invoice_type: "DEB", in_directo: false).where(cancelled_at: nil)
+    new_trans = Invoice.where(in_directo: false).where(cancelled_at: nil)
     total     = new_trans.count
     counter   = 0
     Rails.logger.info("[DIRECTO] Will try to send #{total} invoices")

app/models/invoice.rb

@@ -27,7 +27,7 @@ class Invoice < ActiveRecord::Base
   attr_accessor :billing_email
   validates :billing_email, email_format: { message: :invalid }, allow_blank: true
 
-  validates :invoice_type, :due_date, :currency, :seller_name,
+  validates :due_date, :currency, :seller_name,
             :seller_iban, :buyer_name, :invoice_items, :vat_prc, presence: true
 
   before_create :set_invoice_number, :check_vat

app/models/registrar.rb

@@ -76,7 +76,6 @@ class Registrar < ActiveRecord::Base
   # rubocop:disable Metrics/AbcSize
   def issue_prepayment_invoice(amount, description = nil)
     invoices.create(
-      invoice_type: 'DEB',
       due_date: (Time.zone.now.to_date + Setting.days_to_keep_invoices_active.days).end_of_day,
       payment_term: 'prepayment',
       description: description,