Draft: Add Email Notifications - Scheduled / On-Demand + Coordinator Notification Email

Description

• Raise request updates are sent to the requestee upon approval/rejection
• Button for coordinator to remind teachers of unhandled applications
• Automated emails to remind teachers of unhandled applications/declarations after deadline
• Adds another email address field option for coordinators to send notifications to

Related Issues

• Resolves #141
• Resolves #184

Checklist

• I have added a changelog entry to reflect the significant changes I made.