[FIX] purchase: truncate description for stock.move.line

Before this commit, when creating a PO line with a description that was long
enough (~2712 bytes long) and then confirming the PO, a traceback would
pop up with an error from postgres "index row size exceeds maximum".

This is because when confirming a PO, a stock.move is created with a
stock.move.line mirroring the purchase.order.line, however the "name"
field on stock.move.line is indexed (whereas the purchase.order.line is
not), thus triggering the aforementioned error.

This commit solves this issue by truncating the name field on the
stock.move.line to 2000 bytes (for simplicity's sake) upon creation.

Fixes #33549

closes odoo/odoo#33607

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>

addons/purchase/models/purchase.py

@@ -722,7 +722,9 @@ class PurchaseOrderLine(models.Model):
         for move in self.move_ids.filtered(lambda x: x.state != 'cancel' and not x.location_dest_id.usage == "supplier"):
             qty += move.product_uom._compute_quantity(move.product_uom_qty, self.product_uom, rounding_method='HALF-UP')
         template = {
-            'name': self.name or '',
+            # truncate to 2000 to avoid triggering index limit error
+            # TODO: remove index in master?
+            'name': (self.name or '')[:2000],
             'product_id': self.product_id.id,
             'product_uom': self.product_uom.id,
             'date': self.order_id.date_approve,