[FIX] payment: Keep session serializable
[FIX] payment: Keep session serializable

Fix error like "TypeError: {4} is not JSON serializable" when
serializing the session object (e.g. for external storage)

closes odoo/odoo#41360

X-original-commit: e91e38fa4bd12ba9d2027e7778a10252e08b9a86
Signed-off-by: Damien Bouvy (dbo) <26cc0816b78fc1f1d6597524ae2f7230dc232c77@odoo.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo