[ADD] sale_order_zero_stock_blockage: add manager approval on insufficient stock

Currently, a sales user can confirm a Quotation even if it contains no
products or if the products have insufficient stock compared to the
order quantity. This leads to the creation of invalid Sales Orders,
which negatively impacts inventory planning and invoicing.

This module introduces a validation to the Sales Order confirmation
process to prevent these issues.

The following checks are added:
1. Prevent confirmation if the order has no lines.
2. Prevent confirmation if the product stock is insufficient.

To bypass the insufficient stock restriction, a user with the 'Sales Manager'
group must enable the new 'Approval' (zero_stock_approval) field on the
order.

Technical details:
- Model `sale.order`: Added `zero_stock_approval` Boolean field.
- Method `fields_get`: Overridden to set `zero_stock_approval` as
  readonly for users who are not in the `sales_team.group_sale_manager` group.
- Method `action_confirm`: Added logic to raise a `UserError` if:
    - The order has no lines.
    - A product's `qty_available` is less than `product_uom_qty` (for
      goods) and the `zero_stock_approval` is not enabled.

Task-5382939

Author: danal-odoo

sale_order_zero_stock_blockage/__init__.py

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+from . import models

sale_order_zero_stock_blockage/__manifest__.py

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+{
+    "name": "Sale Order Zero Stock Blockage",
+    "description": """
+    Zero Stock Blockage is module to prevent order to confirm if product is out of stock.
+
+    But if manager wants then he can aprove that order.
+    """,
+    "version": "1.0",
+    "depends": ['sale_management', 'stock'],
+    "author": "danal",
+    "category": "Category",
+    "license": "LGPL-3",
+    "data": [
+        "views/sale_order_view.xml",
+    ],
+}

sale_order_zero_stock_blockage/models/__init__.py

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+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from . import sale_order

sale_order_zero_stock_blockage/models/sale_order.py

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+from odoo.exceptions import UserError
+
+from odoo import fields, models, api
+
+
+class SaleOrder(models.Model):
+    _inherit = 'sale.order'
+
+    zero_stock_approval = fields.Boolean(string="Approval", copy=False)
+
+    @api.model
+    def fields_get(self, allfields=None, attributes=None):
+        res = super().fields_get(allfields, attributes)
+        if not self.env.user.has_group("sales_team.group_sale_manager"):
+            if "zero_stock_approval" in res:
+                res["zero_stock_approval"]["readonly"] = True
+        return res
+
+    def action_confirm(self):
+        for record in self:
+            if not record.order_line:
+                raise UserError("You cannot confirm a Quotation without any products.")
+            if record.zero_stock_approval:
+                return super().action_confirm()
+            for line in record.order_line:
+                if (
+                    line.product_id.qty_available < line.product_uom_qty
+                    and line.product_id.type == "consu"
+                    and not record.zero_stock_approval
+                    and not self.env.user.has_group("sales_team.group_sale_manager")
+                ):
+                    raise UserError(
+                        "Cannot confirm this Sale Order due to insufficient stock.\n\nPlease get approval or adjust the quantities."
+                    )
+        return super().action_confirm()

sale_order_zero_stock_blockage/views/sale_order_view.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<odoo>
+    <record id="sale_order_view_inherit" model="ir.ui.view">
+        <field name="name">sale.order.view.inherit</field>
+        <field name="model">sale.order</field>
+        <field name="inherit_id" ref="sale.view_order_form"/>
+        <field name="arch" type="xml">
+            <xpath expr="//field[@name='payment_term_id']" position="after">
+                <field name="zero_stock_approval"/>
+            </xpath>
+        </field>
+    </record>
+</odoo>