Add loading status indicator in cancel button

aleksis/apps/chronos/frontend/components/substitutions/SubstitutionCard.vue

@@ -43,7 +43,7 @@ import createOrPatchMixin from "aleksis.core/mixins/createOrPatchMixin.js";
         </template>
       </v-autocomplete>
 
-      <delete-button color="red white--text" outlined @click="toggleCancel">{{
+      <delete-button color="red white--text" outlined :loading="loading" @click="toggleCancel">{{
         substitution.cancelled
           ? $t("chronos.substitutions.overview.cancel.decancel")
           : $t("chronos.substitutions.overview.cancel.cancel")