Display errors in frontend

aleksis/apps/paweljong/frontend/components/event_registration/EventRegistrationForm.vue

@@ -597,6 +597,7 @@ import SecondaryActionButton from "aleksis.core/components/generic/buttons/Secon
                     @confirm="mutate"
                     :next-loading="loading"
                   />
+                  <v-alert v-if="error" type="error" outlined>{{ error.message }}</v-alert>
                 </template>
               </ApolloMutation>
             </v-stepper-content>