EmailSender failed emails

[niraymak]

Is your feature request related to a problem? Please describe.
The JobScheduler now receives data from the API in the GraduationWorker. The data contains data about expiring users.
Thereafter the data is forwarded to the Email Sender and most likely the user is informed.

There is a possibility the email is not send for some reason. The EmailSender class does return the response of SendGrid but nothing is done with the response.
https://github.com/DigitalExcellence/dex-backend/blob/develop/NotificationSystem/Services/EmailSender.cs

Describe the solution you'd like
Investigate what we can do with emails that are failed to send.

Production URL

Additional context