[IMP] event_generate_quotation_from_registration: add link to registration in generated sale order and invoice

diplay this link in tree and form views

event_generate_quotation_from_registration/models/account_move.py

@@ -0,0 +1,6 @@
+from odoo import _, api, Command, fields, models
+
+class AccountMove(models.Model):
+    _inherit = "account.move"
+
+    event_registration_id = fields.Many2one('event.registration', string="Stagiaire")