introduce TRPC and service layer

lib/services/util.service.ts

@@ -0,0 +1,10 @@
+export class UtilService {
+  public static addMonths(date: Date, months: number): Date {
+    const d = date.getDate();
+    date.setMonth(date.getMonth() + +months);
+    if (date.getDate() != d) {
+      date.setDate(0);
+    }
+    return date;
+  }
+}