Resolve "substitution planning "cancelled" checkbox does not have false as value when unchecked actively"

Closes #241 (closed)

aleksis/apps/chronos/frontend/components/AmendLesson.vue

@@ -65,7 +65,7 @@
       </template>
       <!-- eslint-disable-next-line vue/valid-v-slot -->
       <template #cancelled.field="{ attrs, on }">
-        <v-checkbox v-bind="attrs" v-on="on" />
+        <v-checkbox :false-value="false" v-bind="attrs" v-on="on" />
       </template>
       <!-- eslint-disable-next-line vue/valid-v-slot -->
       <template #comment.field="{ attrs, on }">
@@ -154,11 +154,15 @@ export default {
   },
   methods: {
     transformCreateData(item) {
+      let { cancelled, ...createItem } = item;
       return {
-        ...item,
+        ...createItem,
         amends: this.selectedEvent.meta.id,
         datetimeStart: this.selectedEvent.startDateTime.toUTC().toISO(),
         datetimeEnd: this.selectedEvent.endDateTime.toUTC().toISO(),
+        // Normalize cancelled, v-checkbox returns null & does not
+        // honor false-value.
+        cancelled: cancelled ? true : false,
       };
     },
     transformPatchData(item) {