[IMP] account: compute foreign amount on bank transactions

With this commit, we improve the usability of foreign bank transactions.
When capturing a new bank transaction (account.bank.statement.line)
- when capturing a new transaction we compute the amount currency based on the transaction date, amount in journal/company currency, and foreign currency
- when the foreign currency is removed, the amount_currency is cleared

Task-3338560
Task-3338532

closes odoo/odoo#122595

X-original-commit: 737c7d26c415b5a136635ef3e4d33d086961c4da
Related: odoo/enterprise#41532
Signed-off-by: Laurent Smet <las@odoo.com>

addons/account/models/account_bank_statement_line.py

@@ -94,6 +94,7 @@ class AccountBankStatementLine(models.Model):
         help="The optional other currency if it is a multi-currency entry.",
     )
     amount_currency = fields.Monetary(
+        compute='_compute_amount_currency', store=True, readonly=False,
         string="Amount in Currency",
         currency_field='foreign_currency_id',
         help="The amount expressed in an optional other currency if it is a multi-currency entry.",
@@ -147,6 +148,19 @@ class AccountBankStatementLine(models.Model):
     # COMPUTE METHODS
     # -------------------------------------------------------------------------
 
+    @api.depends('foreign_currency_id', 'date', 'amount', 'company_id')
+    def _compute_amount_currency(self):
+        for st_line in self:
+            if not st_line.foreign_currency_id or not st_line.date:
+                st_line.amount_currency = False
+            else:
+                st_line.amount_currency = st_line.currency_id._convert(
+                    from_amount=st_line.amount,
+                    to_currency=st_line.foreign_currency_id,
+                    company=st_line.company_id,
+                    date=st_line.date,
+                )
+
     @api.depends('journal_id.currency_id')
     def _compute_currency_id(self):
         for st_line in self: