Member billing, improve invoice display title

This patch improves how membership invoice title are displayed to include the
membership fiscal year and the number of the billing year division.

The shop order invoice title are also made shorter.

app/helpers/invoices_helper.rb

@@ -10,6 +10,12 @@ def entity_type_collection
   def display_entity(invoice, link: true)
     if link && invoice.entity
       auto_link invoice.entity
+    elsif invoice.entity_type == "Membership"
+      t("billing.membership_entity",
+        fiscal_year: invoice.entity.fiscal_year,
+        number: invoice.memberships_amount_description[/#\d+\z/])
+    elsif invoice.entity_type == "Shop::Order"
+      t("shop.title")
     else
       t_invoice_entity_type(invoice.entity_type)
     end

config/locales/billing.yml

@@ -56,6 +56,11 @@ _:
         _en: 'Quarterly billing #%{number}'
         _fr: 'Facturation trimestrielle #%{number}'
         _it: 'Fatturazione trimestrale #%{number}'
+    membership_entity:
+      _de: Abo. %{fiscal_year} %{number}
+      _en: Membership %{fiscal_year} %{number}
+      _fr: Abo. %{fiscal_year} %{number}
+      _it: Abbo. %{fiscal_year} %{number}
     memberships_total:
       _de: Abonnements gesamt
       _en: Total memberships