Get docsByDay out of template and use it as state in the component

This is the foundation of continuous loading (fetchMore).

aleksis/apps/alsijil/frontend/components/coursebook/Coursebook.vue

@@ -6,6 +6,7 @@
     :enable-create="false"
     :enable-edit="false"
     :elevated="false"
+    @items="docsByDay = groupDocsByDay($event)"
     @lastQuery="lastQuery = $event"
     ref="iterator"
     disable-pagination
@@ -15,9 +16,9 @@
     <template #additionalActions="{ attrs, on }">
       <coursebook-filters v-model="filters" />
     </template>
-    <template #default="{ items }">
+    <template #default>
       <v-list-item
-        v-for="day in groupDocsByDay(items)"
+        v-for="day in docsByDay"
         two-line
         :key="'day-' + day[0]"
         :id="'documentation_' + day[0].toISODate()"
@@ -101,6 +102,7 @@ export default {
   data() {
     return {
       gqlQuery: documentationsForCoursebook,
+      docsByDay: {},
       lastQuery: null,
       // Placeholder values while query isn't completed yet
       groups: [],