ExternalExam
  term TermId
  school SchoolId
  courseName (CI Text)
  examName (CI Text)
  defaultTime UTCTime Maybe
  showGrades Bool
  UniqueExternalExam term school courseName examName
ExternalExamResult
  user UserId
  exam ExternalExamId
  result ExamResultGrade
  time UTCTime
  lastChanged UTCTime
  UniqueExternalExamResult exam user
ExternalExamStaff
  user UserId
  exam ExternalExamId
  UniqueExternalExamStaff exam user
ExternalExamOfficeSchool
  school SchoolId
  exam ExternalExamId
  UniqueExternalExamOfficeSchool exam school