[Feature Request] Customizable Email Notifications #9663

Server (please complete the following information):

• Snipe-IT Version: 4.9.5
• OS: [e.g. Ubuntu, CentOS]: ubuntu16.04 (Docker)
• Web Server: [e.g. Apache, IIS]: Apache
• PHP Version: 7.1.33

Is your feature request related to a problem? Please describe.
I have seen some requests similar to this asking for specific email notifications, but would like something more broad. We had an issue today where users reported getting reminders about expected checkin but are not wanting this for staff. We had to change some code and manipulate data to get this to stop. Could not find a way from the front end to disable the expected checkin email or to set how many days prior to expected checkin to set the trigger to.

Describe the solution you'd like
Would like to see a gui interface to create customizable email notifications so that any and all notifications sent from the system can be modified easily and new ones created.

Describe alternatives you've considered
Alternative is to change data or code or both on the back end to accommodate existing email notifications or use an integration with another platform that can send mass emails (we do use CloverDX that can pull from the mysql database and populate and send emails).

Additional context
Add any other context or screenshots about the feature request here.