[FIX] project: make personal stage non required in task form view

Since https://github.com/odoo/odoo/pull/90588, the personal stage is a required field in the task form view in debug mode.
However, we only generate personal stage for a given user when that user is first assigned to a task.
If a user creates their first task and assign it to themselves, they won't be able to give it a personal stage.

To prevent issues linked to the current users not having personal stages, this commit makes the field not required, but prevents the user from unsetting it

closes odoo/odoo#99735

Signed-off-by: Laurent Stukkens (ltu) <ltu@odoo.com>

addons/project/models/project.py

@@ -2043,6 +2043,9 @@ class Task(models.Model):
         # Track user_ids to send assignment notifications
         old_user_ids = {t: t.user_ids for t in self}
 
+        if "personal_stage_type_id" in vals and not vals['personal_stage_type_id']:
+            del vals['personal_stage_type_id']
+
         result = super(Task, tasks).write(vals)
 
         if 'user_ids' in vals:

addons/project/views/project_views.xml

@@ -1300,7 +1300,7 @@
                                 <group>
                                     <field name="is_analytic_account_id_changed" invisible="1"/>
                                     <field name="parent_id" attrs="{'invisible': [('allow_subtasks', '=', False)]}" groups="base.group_no_one"/>
-                                    <field name="personal_stage_type_id" string="Personal Stage" groups="base.group_no_one" domain="[('user_id', '!=', False)]" context="{'default_user_id' : uid}" readonly="0" required="1" attrs="{'invisible': &quot;[('user_ids', 'not in', [uid])]&quot;}"/>
+                                    <field name="personal_stage_type_id" string="Personal Stage" groups="base.group_no_one" domain="[('user_id', '!=', False)]" context="{'default_user_id' : uid}" readonly="0" attrs="{'invisible': &quot;[('user_ids', 'not in', [uid])]&quot;}"/>
                                     <field name="analytic_account_id" groups="analytic.group_analytic_accounting" context="{'default_partner_id': partner_id}"/>
                                     <field name="analytic_tag_ids" groups="analytic.group_analytic_tags" widget="many2many_tags"/>
                                     <field name="company_id" groups="base.group_multi_company" options="{'no_create': True}"/>