Organizer shift schedule

[Auriosi]

• Admins should be able to add a shift and select what organizers are assigned to it
  • Optionally, admin should be able to specify custom start and end time per person for reduced shifts
• Shift schedule page should be available to all organizers, default to showing what their shift schedule looks like
  • If they so desire, organizers should also be able to see the overall shift schedule
• Organizers (with their Discord linked) should receive a DM notification shortly before their shift begins