User can get notification about activity on email (24)

[denyskom]

Criteria

• user should receive notification about all activities planned for today in the morning
• user should receive notification 15 minutes before activity, if time is indicated
• user can see styled email message
• user shouldn't receive notification, if activity time passed

Tasks

• add delivery manager (mailgun for example) (3) (4)
• add domain to mailgun and DNS records to verify it (2)
  *Note it can take 24-48 hours for DNS changes to propagate
• add scheduler that will run mailing method (2)(4)
• query all activities and user they assigned to (get activity, and user email) (2) (3)
• create massage template (6)
  
• form message based on activity and add delivery time to it (2)(3)
• send information to delivery manager (2) (2)
• create method that will check, all activities for next 15 minutes (1)(2)
• add fixation in db about delivered notifications (1)
• add tests (2)