[FIX] contract: remove groupby if it is in context + consistency between contract count and contract action

On the commercial entity, the count shows all contracts of child partners.
However clicking on the action might show no contract, as the action only
restricted the domain to the partner itself.
We extract the domain into a function to share it in both cases.

Co-authored by @Lopsanz

contract/models/res_partner.py

@@ -17,10 +17,14 @@ class ResPartner(models.Model):
         comodel_name="contract.contract", inverse_name="partner_id", string="Contracts",
     )
 
+    def _get_partner_contract_domain(self):
+        self.ensure_one()
+        return [("partner_id", "child_of", self.ids)]
+
     def _compute_contract_count(self):
         contract_model = self.env["contract.contract"]
         fetch_data = contract_model.read_group(
-            [("partner_id", "child_of", self.ids)],
+            self._get_partner_contract_domain(),
             ["partner_id", "contract_type"],
             ["partner_id", "contract_type"],
             lazy=False,
@@ -50,14 +54,11 @@ class ResPartner(models.Model):
         contract_type = self._context.get("contract_type")
 
         res = self._get_act_window_contract_xml(contract_type)
-        res.update(
-            context=dict(
-                self.env.context,
-                search_default_partner_id=self.id,
-                default_partner_id=self.id,
-                default_pricelist_id=self.property_product_pricelist.id,
-            ),
-        )
+        action_context = {k: v for k, v in self.env.context.items() if k != "group_by"}
+        action_context["domain"] = self._get_partner_contract_domain()
+        action_context["default_partner_id"] = self.id
+        action_context["default_pricelist_id"] = self.property_product_pricelist.id
+        res["context"] = action_context
         return res
 
     def _get_act_window_contract_xml(self, contract_type):