Add a backend-common package with common concerns such as logging

packages/backend/package.json

@@ -15,6 +15,7 @@
     "clean": "backstage-cli clean"
   },
   "dependencies": {
+    "@backstage/backend-common": "0.1.1-alpha.4",
     "@backstage/plugin-inventory-backend": "0.1.1-alpha.4",
     "compression": "^1.7.4",
     "cors": "^2.8.5",
@@ -28,6 +29,7 @@
     "@types/express": "^4.17.6",
     "@types/express-serve-static-core": "^4.17.5",
     "@types/helmet": "^0.0.45",
+    "jest": "^25.1.0",
     "tsc-watch": "^4.2.3",
     "typescript": "^3.8.3"
   },