Define statistics queries (by person & by group)

aleksis/apps/alsijil/frontend/components/coursebook/statistics/statistics.graphql

+fragment statistics on StatisticsByPersonType {
+  participationCount
+  absenceCount
+  absenceReasons {
+    id
+    shortName
+    name
+    colour
+    countAsAbsent
+    count
+  }
+  tardinessSum
+  tardinessCount
+  extraMarks {
+    id
+    shortName
+    name
+    colourFg
+    colourBg
+    showInCourseBook
+    count
+  }
+}
+
+query statisticsByPerson (
+  $personId: ID!
+  $termId: ID!
+) {
+  statistics: statisticsByPerson(
+    $personId: ID!
+    $termId: ID!
+  ) {
+  ...statistics
+}
+
+query statisticsByGroup (
+  $groupId: ID!
+  $termId: ID!
+) {
+  statistics: statisticsByGroup(
+    $groupId: ID!
+    $termId: ID!
+  ) {
+  persons {
+    id
+    firstName
+    lastName
+    ...statistics
+  }
+}