WIP Added model, migration and bulk upsert fnc.

app/migrations/20200121094500-add-constraint-priceHistory.js

@@ -0,0 +1,10 @@
+"use strict";
+module.exports = {
+  up: (queryInterface, Sequelize) =>
+    queryInterface.addConstraint("PriceHistory", ["realEstateId", "price"], {
+      type: "unique",
+      name: "uniquePriceRealEstate"
+    }),
+  down: queryInterface =>
+    queryInterface.removeConstraint("PriceHistory", "uniquePriceRealEstate")
+};