Add dependency Injection

Repositories/IGerbilRepository.cs

@@ -0,0 +1,11 @@
+using GerbilManager.Models;
+
+namespace GerbilManager.Repositories
+{
+    public interface IGerbilRepository
+    {
+        IEnumerable<Gerbil> GetGerbils();
+
+        Gerbil GetGerbil(Guid id);
+    }
+}

Repositories/InMemGerbilRepository.cs

@@ -2,8 +2,7 @@ using GerbilManager.Models;
 
 namespace GerbilManager.Repositories
 {
-
-    public class InMemGerbilRepository
+    public class InMemGerbilRepository : IGerbilRepository
     {
         private readonly List<Gerbil> _gerbilList = new()
         {
@@ -19,5 +18,5 @@ namespace GerbilManager.Repositories
 
         public Gerbil GetGerbil(Guid id) => _gerbilList.SingleOrDefault(x => x.Id == id);
     }
-    
+
 }