feat(TestBase): seed real email templates in TestBase setup

- Added `RealEmailTemplates` property with predefined email templates.
- Populated the repository with these templates in the `Setup` method.
- Ensures tests have consistent, realistic email data available.

EnvelopeGenerator.Application/Common/Notifications/DocSigned/Handlers/HistoryHandler.cs

@@ -30,9 +30,8 @@ public class HistoryHandler : INotificationHandler<DocSignedNotification>
     /// <returns></returns>
     public async Task Handle(DocSignedNotification notification, CancellationToken cancel)
     {
-        if(notification.Receiver is null)
-            if (notification.Receiver is null)
-                throw new InvalidOperationException($"Receiver information is missing in the notification. DocSignedNotification:\n {notification.ToJson(Format.Json.ForDiagnostics)}");
+        if (notification.Receiver is null)
+            throw new InvalidOperationException($"Receiver information is missing in the notification. DocSignedNotification:\n {notification.ToJson(Format.Json.ForDiagnostics)}");
 
         await _sender.Send(new CreateHistoryCommand()
         {

EnvelopeGenerator.Application/Common/Notifications/SendMailHandler.cs

@@ -99,8 +99,8 @@ public abstract class SendMailHandler<TNotification> : INotificationHandler<TNot
         var placeHolders = CreatePlaceHolders(notification);
 
         var temp = await TempRepo
-            .ReadOnly()
-            .SingleOrDefaultAsync(x => x.Name == notification.TemplateType.ToString(), cancel)
+            .Where(x => x.Name == notification.TemplateType.ToString())
+            .SingleOrDefaultAsync(cancel)
                 ?? throw new InvalidOperationException($"Receiver information is missing in the notification." +
                 $"{typeof(TNotification)}:\n {notification.ToJson(Format.Json.ForDiagnostics)}");