Admin controller, Locations controller, requests to add available countries, request to get available countries

SchengenVisaApi/Domains/LocationDomain/City.cs

@@ -1,4 +1,6 @@
-namespace Domains.LocationDomain;
+using System.Text.Json.Serialization;
+
+namespace Domains.LocationDomain;
 
 /// Model of a city
 public class City : IEntity
@@ -10,5 +12,6 @@ public class City : IEntity
     public string Name { get; set; } = null!;
 
     /// <see cref="LocationDomain.Country"/> in which the city is located
+    [JsonIgnore]
     public Country Country { get; set; } = null!;
-}
+}