consolidate Service interface and implementation classes

Oqtane.Client/Services/TenantService.cs

@@ -8,6 +8,25 @@ using Oqtane.Shared;
 
 namespace Oqtane.Services
 {
+    /// <summary>
+    /// Service to manage <see cref="Tenant"/>s on the Oqtane installation.
+    /// </summary>
+    public interface ITenantService
+    {
+        /// <summary>
+        /// Get all <see cref="Tenant"/>s
+        /// </summary>
+        /// <returns></returns>
+        Task<List<Tenant>> GetTenantsAsync();
+
+        /// <summary>
+        /// Get one specific <see cref="Tenant"/>
+        /// </summary>
+        /// <param name="tenantId">ID-reference of the <see cref="Tenant"/></param>
+        /// <returns></returns>
+        Task<Tenant> GetTenantAsync(int tenantId);
+    }
+
     [PrivateApi("Don't show in the documentation, as everything should use the Interface")]
     public class TenantService : ServiceBase, ITenantService
     {