Fix dialog-Object-Form's internal dialog-mode-handling

and move to proper places.

Now the dialog-mode can be set from parent via v-model and from child via #activator. The later was previously broken.

The new placement just makes more sense with the mixins.

aleksis/core/frontend/components/generic/dialogs/DialogObjectForm.vue

 <template>
   <mobile-fullscreen-dialog
-    v-model="dialog"
+    v-model="dialogMode"
     max-width="555px"
     :close-button="false"
   >
@@ -26,7 +26,7 @@
         :valid.sync="valid"
         @loading="handleLoading"
         @save="handleSave"
-        @cancel="dialog = false"
+        @cancel="dialogMode = false"
       >
         <template v-for="(_, slot) of $scopedSlots" #[slot]="scope"
           ><slot :name="slot" v-bind="scope"
@@ -35,7 +35,7 @@
     </template>
 
     <template #actions>
-      <cancel-button @click="dialog = false" :disabled="loading" />
+      <cancel-button @click="dialogMode = false" :disabled="loading" />
       <save-button
         @click="$refs.form.submit()"
         :loading="loading"
@@ -67,22 +67,9 @@ export default {
   },
   mixins: [openableDialogMixin, objectFormPropsMixin, loadingMixin],
   emits: ["cancel", "save"],
-  computed: {
-    dialog: {
-      get() {
-        return this.value;
-      },
-      set(newValue) {
-        this.$emit("input", newValue);
-      },
-    },
-  },
   methods: {
-    close() {
-      this.dialog = false;
-    },
     handleSave(items) {
-      this.dialog = false;
+      this.dialogMode = false;
       this.$emit("save", items);
     },
   },