Add schema, logic for importing CORE VendorItem -> ProductCost

rattail_corepos/db/model/__init__.py

@@ -26,4 +26,4 @@ Database schema extensions for CORE-POS integration
 
 from .people import CorePerson, CoreCustomer, CoreMember
 from .products import (CoreDepartment, CoreSubdepartment,
-                       CoreVendor, CoreProduct)
+                       CoreVendor, CoreProduct, CoreProductCost)

rattail_corepos/db/model/products.py

@@ -168,3 +168,38 @@ class CoreProduct(model.Base):
         return str(self.product)
 
 CoreProduct.make_proxy(model.Product, '_corepos', 'corepos_id')
+
+
+class CoreProductCost(model.Base):
+    """
+    CORE-specific extensions to :class:`rattail:rattail.db.model.ProductCost`.
+    """
+    __tablename__ = 'corepos_product_cost'
+    __table_args__ = (
+        sa.ForeignKeyConstraint(['uuid'], ['product_cost.uuid'],
+                                name='corepos_product_cost_fk_cost'),
+    )
+    __versioned__ = {}
+
+    uuid = model.uuid_column(default=None)
+    cost = orm.relationship(
+        model.ProductCost,
+        doc="""
+        Reference to the actual ProductCost record, which this one extends.
+        """,
+        backref=orm.backref(
+            '_corepos',
+            uselist=False,
+            cascade='all, delete-orphan',
+            doc="""
+            Reference to the CORE-POS extension record for this product cost.
+            """))
+
+    corepos_id = sa.Column(sa.Integer(), nullable=False, doc="""
+    ``vendorItemID`` value for the corresponding record within CORE-POS.
+    """)
+
+    def __str__(self):
+        return str(self.cost)
+
+CoreProductCost.make_proxy(model.ProductCost, '_corepos', 'corepos_id')