[UPD] update partner form view for user_id field

views/res_partner.xml

 <?xml version="1.0" encoding="utf-8" ?>
 <odoo>
     <data>
+        <!-- Form View -->
+        <record id="view_res_partner_form_inherit" model="ir.ui.view">
+            <field name="name">res.partner.form</field>
+            <field name="model">res.partner</field>
+            <field name="inherit_id" ref="base.view_partner_form" />
+            <field name="priority" eval="90" />
+            <field name="arch" type="xml">
+                <xpath expr="//group[@name='sale']/field[@name='user_id']" position="attributes">
+                    <attribute name="readonly">1</attribute>
+                </xpath>
+                <xpath expr="//group[@name='sale']/field[@name='user_id']" position="after">
+                    <field
+                        name="user_id"
+                        string="Vendeur (config)"
+                        groups="base.group_erp_manager"
+                    />
+                </xpath>
+            </field>
+        </record>
 
+        <!-- Search View -->
         <record id="view_res_partner_filter_inherit" model="ir.ui.view">
             <field name="name">res.partner.select</field>
             <field name="model">res.partner</field>