[IMP] website_crm_partner_assign: consider assigned partner for stat button

Currently the 'Opportunities' stat button on partner form view does not show
the opportunities where current partner is assigned one, it only shows the
ones that have current partner(and it's children) set as a customer.

This commit includes such opportunities (where current partner is set as
assigned parter) in the count of stat button and on the view we get when
clicking this button.

taskID-2443894
closes https://github.com/odoo/odoo/pull/67524

Part-of: odoo/odoo#67524

addons/website_crm_partner_assign/models/res_partner.py

@@ -2,6 +2,7 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
 from odoo import api, fields, models
+from odoo.osv import expression
 from odoo.addons.http_routing.models.ir_http import slug
 
 
@@ -79,3 +80,20 @@ class ResPartner(models.Model):
     def _compute_partner_weight(self):
         for partner in self:
             partner.partner_weight = partner.grade_id.partner_weight if partner.grade_id else 0
+
+    def _compute_opportunity_count(self):
+        super()._compute_opportunity_count()
+        assign_counts = {}
+        if self.ids:
+            opportunity_data = self.env['crm.lead'].with_context(active_test=False).read_group(
+                [('partner_assigned_id', 'in', self.ids)],
+                ['partner_assigned_id'], ['partner_assigned_id']
+            )
+            assign_counts = {datum['partner_assigned_id'][0]: datum['partner_assigned_id_count'] for datum in opportunity_data}
+        for partner in self:
+            partner.opportunity_count += assign_counts.get(partner.id, 0)
+
+    def action_view_opportunity(self):
+        action = super().action_view_opportunity()
+        action['domain'] = expression.OR([action.get('domain', []), [('partner_assigned_id', '=', self.id)]])
+        return action