Purchase Reception Notify

This module adds an automatic notification on purchase orders when goods are actually received in stock.

• When a receipt (an incoming shipment) is validated, Odoo posts a message on each related purchase order. The message shows the receipt reference and a list of the products received with their quantities and units of measure.
• The message is sent using a dedicated message type called "Purchase Receptions", so followers can choose to receive or mute these notifications separately from other purchase order messages.
• This message type is internal by default, meaning it is visible to employees but not to external followers such as portal users.
• The notification is posted on the purchase order, not on the shipment, and it is attributed to the user who validated the receipt.
• Only incoming shipments are handled; outgoing or internal transfers are ignored.
• On installation, the module also subscribes existing followers of purchase orders to this new message type, but only for followers who are still active employees.

It touches the stock.picking model (incoming receipts) and the purchase.order model through messages and followers. There are no new menus or screens: everything happens through the standard chatter on purchase orders.