Add method on location to fetch a tray

* Add vertical_lift_shuttle_id field on stock.location, help to find the
shuttle for a location
* Add StockLocation.fetch_vertical_lift_tray(), that needs to be
implemented in addons to send commands to the hardward to fetch a tray,
and if existing show a cell (laser pointer, ...)
* Add helpers on stock.move.line fetch_vertical_lift_tray_source() and
fetch_vertical_lift_tray_dest() that fetch the tray directly from a move
line's source or destination location

stock_vertical_lift_kardex/models/__init__.py

@@ -1 +1,2 @@
+from . import stock_location
 from . import vertical_lift_shuttle

stock_vertical_lift_kardex/models/stock_location.py

@@ -0,0 +1,56 @@
+# Copyright 2019 Camptocamp SA
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+import logging
+from odoo import models
+
+_logger = logging.getLogger(__name__)
+
+
+class StockLocation(models.Model):
+    _inherit = 'stock.location'
+
+    def _hardware_kardex_prepare_payload(self, cell_location=None):
+        return ""
+
+    def _hardware_vertical_lift_tray(self, cell_location=None):
+        """Send instructions to the vertical lift hardware
+
+        Private method, this is where the implementation actually happens.
+        Addons can add their instructions based on the hardware used for
+        this location.
+
+        The hardware used for a location can be found in:
+
+        ``self.vertical_lift_shuttle_id.hardware``
+
+        Each addon can implement its own mechanism depending of this value
+        and must call ``super``.
+
+        The method must send the command to the vertical lift to fetch / open
+        the tray. If a ``cell_location`` is passed and if the hardware supports
+        a way to show a cell (such as a laser pointer), it should send this
+        command as well.
+
+        Useful information that could be needed for the drivers:
+
+        * Any field of `self` (name, barcode, ...) which is the current tray.
+        * Any field of `cell_location` (name, barcode, ...) which is the cell
+          in the tray.
+        * ``self.vertical_lift_shuttle_id`` is the current Shuttle, where we
+          find details about the hardware, the current mode (pick, put, ...).
+        * ``self.tray_type_id`` is the kind of tray.
+        * ``self.tray_type_id.width_per_cell`` and
+          ``self.tray_type_id.depth_per_cell`` return the size of a cell in mm.
+        * ``cell_location.posx`` and ``posy`` are the coordinate from the
+          bottom-left of the tray.
+        * ``cell_location.tray_cell_center_position()`` returns the central
+          position of the cell in mm from the bottom-left of a tray. (distance
+          from left, distance from bottom). Can be used for instance for
+          highlighting the cell using a laser pointer.
+        """
+        if self.vertical_lift_shuttle_id.hardware == "kardex":
+            payload = self._hardware_kardex_prepare_payload()
+            _logger.debug("Sending to kardex: {}", payload)
+            # TODO implement the communication with kardex
+        super()._hardware_vertical_lift_tray(cell_location=cell_location)