Private Email Service Support (#1028)

* Added ServerSettingKey's for SMTP and moved email service code to Kavita. Nothing integrated in the UI yet.

* Undo all the custom SMTP stuff and prepare for custom email service url.

* Foundation for email service to use a custom url is setup.

* Implemented the ability to hook up custom email url

API/Extensions/ApplicationServiceExtensions.cs

@@ -39,7 +39,6 @@ namespace API.Extensions
             services.AddScoped<IAccountService, AccountService>();
             services.AddScoped<IEmailService, EmailService>();
 
-
             services.AddScoped<IFileSystem, FileSystem>();
             services.AddScoped<IFileService, FileService>();
             services.AddScoped<ICacheHelper, CacheHelper>();