refactor: arreglado formato de los repositorios

Signed-off-by: fede <federico.nicolas.polidoro@gmail.com>

Modelo/RepositorioBase.cs

@@ -4,12 +4,17 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Modelo;
 
-public abstract class RepositorioBase<T> where T : class, new()
+public abstract class RepositorioBase<T, S>
+    where T : class, new()
+    where S : new()
 {
     protected AlquilaFacilContext Context { get; set; } = new AlquilaFacilContext();
 
     public abstract ReadOnlyCollection<T> Listar();
 
+    private static readonly S  instance = new();
+    public static S Singleton { get{return instance;}}
+
     public bool Guardar(){
         bool ret = false;
         try
@@ -24,5 +29,4 @@ public abstract class RepositorioBase<T> where T : class, new()
         }
         return ret;
     }
-
 }