Add strict tsc flag for the backend ts code (#3355)

tsconfig.backend.json

@@ -9,6 +9,9 @@
     "moduleResolution": "node",
     /* Code generation */
     "outDir": "./out/app",
-    "typeRoots": ["./typings", "./node_modules/@types"]
+    "typeRoots": ["./typings", "./node_modules/@types"],
+    /* Other options */
+    "strict": true,
+    "noImplicitAny": false
   }
 }