feat(notification): add admin rest management and deletion

Add revision-safe service and template APIs, channel mapping, and validated admin controls.

Ref: IT-1601

HrynCo.NotificationService.Web/Controllers/Api/EmailChannels/EmailChannelMapping.cs

@@ -0,0 +1,23 @@
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+
+namespace HrynCo.NotificationService.Web.Controllers.Api.EmailChannels;
+
+internal static class EmailChannelMapping
+{
+    public static SmtpChannelSettings ToSettings(SmtpChannelSettingsDto settings) => new()
+    {
+        Host = settings.Host, Port = settings.Port, Username = settings.Username, Password = settings.Password,
+        UseSsl = settings.UseSsl, FromEmail = settings.FromEmail, FromName = settings.FromName
+    };
+
+    public static EmailChannelDto Map(EmailChannel channel)
+    {
+        var smtp = (SmtpChannelSettings)channel.Settings;
+        return new EmailChannelDto(channel.Id, channel.ServiceName, channel.Priority, channel.EmailChannelType,
+            new SmtpChannelSettingsDto
+            {
+                Host = smtp.Host, Port = smtp.Port, Username = smtp.Username, Password = smtp.Password,
+                UseSsl = smtp.UseSsl, FromEmail = smtp.FromEmail, FromName = smtp.FromName
+            }, channel.DailyLimit, channel.MonthlyLimit, channel.WarnThresholdPercent, channel.IsActive, channel.Created, channel.Updated);
+    }
+}