[FIX] account: prevent draft entry for reconciled statement

Journal entries of a bank statement can be reset to draft even if the
bank statement has been validated

Steps to reproduce:
1. Install Accounting
2. Go to Accounting dashboard, click on the 3 dots of Bank and go to
View > Statements
3. Create a new statement with a transaction of 100, correctly set the
ending balance, save and post
4. Click on reconcile then validate the reconciliation
5. Go back to the statement and validate it
6. Open the journal entry of the statement
7. You can reset it to draft but you shouldn't be able to

Solution:
Prevent the user from resetting a journal entry to draft if the
statement has been confirmed

opw-2827117

closes odoo/odoo#92713

X-original-commit: 5622bc103e063d62f75625ca413a06aa7395d654
Signed-off-by: Laurent Smet <las@odoo.com>
Signed-off-by: Guillaume Merlin (megu) <megu@odoo.com>

addons/account/models/account_bank_statement.py

@@ -904,7 +904,7 @@ class AccountBankStatementLine(models.Model):
             st_line_vals_to_write = {}
 
             if 'state' in changed_fields:
-                if (st_line.state == 'open' and move.state != 'draft') or (st_line.state == 'posted' and move.state != 'posted'):
+                if (st_line.state == 'open' and move.state != 'draft') or (st_line.state in ('posted', 'confirm') and move.state != 'posted'):
                     raise UserError(_(
                         "You can't manually change the state of journal entry %s, as it has been created by bank "
                         "statement %s."

addons/account/tests/test_account_bank_statement.py

@@ -1141,6 +1141,32 @@ class TestAccountBankStatementLine(TestAccountBankStatementCommon):
             {'debit': 0.0,      'credit': 80.0,     'amount_currency': -80.0,       'currency_id': self.currency_1.id},
         )
 
+    def test_reconciliation_move_draft(self):
+        ''' Ensures that the account move of a reconciled statement cannot be set to draft
+        '''
+        statement = self.env['account.bank.statement'].create({
+            'name': 'test_statement',
+            'date': '2019-01-01',
+            'journal_id': self.bank_journal_1.id,
+            'line_ids': [
+                (0, 0, {
+                    'date': '2019-01-01',
+                    'payment_ref': 'line_1',
+                    'partner_id': self.partner_a.id,
+                    'amount': 100.0,
+                }),
+            ],
+        })
+
+        statement.button_post()
+        statement.line_ids[0].reconcile([{'name': 'test', 'account_id': self.company_data['default_account_revenue'].id, 'balance': -100}])
+
+        statement.button_validate_or_action()
+        account_move = statement.line_ids.move_id
+
+        with self.assertRaises(UserError):
+            account_move.button_draft()
+
     def test_reconciliation_statement_line_state(self):
         ''' Test the reconciliation on the bank statement line with a foreign currency on the journal:
         - Ensure the statement line is_reconciled field is well computed.