Added database entities, started with node crud

MoonlightServers.ApiServer/Database/Entities/Allocation.cs

@@ -0,0 +1,12 @@
+namespace MoonlightServers.ApiServer.Database.Entities;
+
+public class Allocation
+{
+    public int Id { get; set; }
+
+    public string IpAddress { get; set; } = "0.0.0.0";
+    public int Port { get; set; }
+
+    public Server? Server { get; set; }
+    public Node Node { get; set; }
+}