[FIX] partner_event: recover missing functionality

In previous versions it was possible to use the registration wizard from
the attendees list. This commit recovers it.

TT45692

partner_event/wizard/res_partner_register_event.py

@@ -31,9 +31,16 @@ def _prepare_registration(self, partner):
     def button_register(self):
         vals_list = []
         Registration = self.env["event.registration"]
-        for partner in self.env["res.partner"].browse(
-            self.env.context.get("active_ids", [])
-        ):
+        active_ids = self.env.context.get("active_ids", [])
+        if self.env.context.get("active_model", "") == "event.registration":
+            partners = (
+                self.env["event.registration"]
+                .browse(active_ids)
+                .mapped("attendee_partner_id")
+            )
+        else:
+            partners = self.env["res.partner"].browse(active_ids)
+        for partner in partners:
             if not Registration.search(
                 [
                     ("event_id", "=", self.event.id),

partner_event/wizard/res_partner_register_event_view.xml

@@ -37,4 +37,12 @@
         <field name="binding_model_id" ref="base.model_res_partner" />
         <field name="target">new</field>
     </record>
+    <record id="action_partner_register_event" model="ir.actions.act_window">
+        <field name="name">Register in an event</field>
+        <field name="res_model">res.partner.register.event</field>
+        <field name="view_mode">form</field>
+        <field name="view_id" ref="res_partner_register_event_view" />
+        <field name="binding_model_id" ref="partner_event.model_event_registration" />
+        <field name="target">new</field>
+    </record>
 </odoo>