[IMP] account_statement_import_camt: multi account support

The module account_statement_import_file supports handling files
containing informations related to multiple accounts, but this was not
taken advantage of by account_statement_import_camt.

We update the structure returned by parser.parse() to use the expected
format in case of multiple accounts encountered in CAMT file.

This has the side effect of fixing a bug in the previous implementation,
when all the transactions in a CAMT file would be parsed as being on the
same account (the one on the last statement found in the file), and
possibly even more wrong, in the currency of the last statement).

account_statement_import_camt/models/parser.py

@@ -2,6 +2,7 @@
 # Copyright 2013-2016 Therp BV <https://therp.nl>
 # Copyright 2017 Open Net Sàrl
 # License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl.html).
+from collections import defaultdict
 import re
 
 from lxml import etree
@@ -444,7 +445,7 @@ def parse(self, data):
             raise ValueError("Not a valid xml file, or not an xml file at all.")
         ns = root.tag[1 : root.tag.index("}")]
         self.check_version(ns, root)
-        statements = []
+        statements = defaultdict(list)
         currency = None
         account_number = None
         for node in root[0][1:]:
@@ -454,5 +455,5 @@ def parse(self, data):
                     currency = statement.pop("currency")
                 if "account_number" in statement:
                     account_number = statement.pop("account_number")
-                statements.append(statement)
-        return currency, account_number, statements
+                statements[(currency, account_number)].append(statement)
+        return [(currency, account_number, statement_list) for (currency, account_number), statement_list in statements.items()]