many fixes and improvements - rework for modules/ and common/

feat(emailer): add Postmark and Resend providers

backend/Modules/Creators/Configuration/CreatorOptions.cs

@@ -0,0 +1,8 @@
+namespace Hutopy.Modules.Creators.Configuration;
+
+public class CreatorOptions
+{
+    public const string ConfigurationSection = "Creators";
+    
+    public TimeSpan SlugReservationDuration { get; set; }
+}