Added comments, changed generic repository, removed warnings

SchengenVisaApi/Infrastructure/Database/GeneralExceptions/EntityNotFoundException.cs

@@ -1,4 +1,10 @@
-namespace Infrastructure.Database.GeneralExceptions
+using Domains;
+
+namespace Infrastructure.Database.GeneralExceptions
 {
-    public class EntityNotFoundException<T>(Guid id) : Exception($"Entity {typeof(T).Name} with id '{id}' not found");
+    /// Exception to throw when entity with specific id not found
+    /// <param name="id">Identifier of entity</param>
+    /// <typeparam name="T">Not found entity type</typeparam>
+    public class EntityNotFoundException<T>(Guid id) : Exception($"Entity {typeof(T).Name} with id '{id}' not found")
+        where T : class, IEntity;
 }