Add admin view:

Users tab:
  - Show registered users and their orders (tree view? table with expandable groupings?) meaning what they created and what they participated in
  - Allow deleting users (and their orders), also add switch to make them admin (popconfirm)
  - View and set user email and confirmed state

E-Mail configuration tab:
  - View email configuration (without password)
  - Ability to send test email