consolidate Infrastructure interface and implementation classes

Oqtane.Server/Infrastructure/TenantManager.cs

@@ -7,6 +7,15 @@ using Oqtane.Shared;
 
 namespace Oqtane.Infrastructure
 {
+    public interface ITenantManager
+    {
+        Alias GetAlias();
+        Tenant GetTenant();
+        void SetAlias(Alias alias);
+        void SetAlias(int tenantId, int siteId);
+        void SetTenant(int tenantId);
+    }
+
     public class TenantManager : ITenantManager
     {
         private readonly IHttpContextAccessor _httpContextAccessor;