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

WebApp/Entities/Message.cs

@@ -0,0 +1,13 @@
+namespace WebApp.Entities
+{
+    public class Message
+    {
+        public int MessageId { get; set; }
+        public int EventType { get; set; }
+        public int VolunteerId { get; set; }
+        public int OrganizationId { get; set; }
+        public bool IsMsgFromVolunteer { get; set; }
+        public DateTime IsoDate { get; set; }
+        public string? Content { get; set; }
+    }
+}