fix: rev db model, added missing entities and helper functions

WebApp/Entities/Token.cs

@@ -0,0 +1,10 @@
+namespace WebApp.Entities
+{
+    public class Token
+    {
+        public int TokenId { get; set; }
+        public required int UserId { get; set; }
+        public required DateTime ValidUntil { get; set; }
+        public string? Value { get; set; }
+    }
+}