[ADD] l10n_ar: use 5 digits pos number instead of 4

The law itself said that you can use 4 or 5 digits, but some customers
complains that they want 5 (for eg. 00001) because some suppliers reject
the invoice if only 4 digits (that is wrong, but suppliers do anything
to avoid paying).

We've check and AFIP online invoices use 5 digits always. So, to satisfy
customers/suppliers and make code simpler, we think using 5 digits is a
better option.

addons/l10n_ar/models/account_journal.py

@@ -189,5 +189,4 @@ class AccountJournal(models.Model):
         we add or not a prefix to identify sales journal.
         """
         if self.type == 'sale' and self.l10n_ar_afip_pos_number:
-            pos_num = str(self.l10n_ar_afip_pos_number)
-            self.code = pos_num if len(pos_num) > 4 else _('S') + "%04d" % self.l10n_ar_afip_pos_number
+            self.code = "%05i" % self.l10n_ar_afip_pos_number

addons/l10n_ar/models/l10n_latam_document_type.py

@@ -38,7 +38,7 @@ class L10nLatamDocumentType(models.Model):
         if self.country_id != self.env.ref('base.ar'):
             return values
 
-        values.update({'padding': 8, 'implementation': 'no_gap', 'prefix': "%04i-" % (journal.l10n_ar_afip_pos_number),
+        values.update({'padding': 8, 'implementation': 'no_gap', 'prefix': "%05i-" % (journal.l10n_ar_afip_pos_number),
                        'l10n_latam_journal_id': journal.id})
         if journal.l10n_ar_share_sequences:
             values.update({'name': '%s - Letter %s Documents' % (journal.name, self.l10n_ar_letter),
@@ -85,9 +85,7 @@ class L10nLatamDocumentType(models.Model):
                 failed = True
             elif len(number) > 8 or not number.isdigit():
                 failed = True
-            if len(pos) == 5 and pos[0] == '0':
-                pos = pos[1:]
-            document_number = '{:>04s}-{:>08s}'.format(pos, number)
+            document_number = '{:>05s}-{:>08s}'.format(pos, number)
         if failed:
             raise UserError(msg % (document_number, self.name, _(
                 'The document number must be entered with a dash (-) and a maximum of 5 characters for the first part'