add missing ui functions

src/www/js/api.js

@@ -138,6 +138,14 @@ class API {
     });
   }
 
+  async updateClientAddress6({ clientId, address6 }) {
+    return this.call({
+      method: 'put',
+      path: `/wireguard/client/${clientId}/address6/`,
+      body: { address6 },
+    });
+  }
+
   async restoreConfiguration(file) {
     return this.call({
       method: 'put',

src/www/js/app.js

@@ -301,6 +301,11 @@ new Vue({
         .catch((err) => alert(err.message || err.toString()))
         .finally(() => this.refresh().catch(console.error));
     },
+    updateClientAddress6(client, address6) {
+      this.api.updateClientAddress6({ clientId: client.id, address6 })
+        .catch((err) => alert(err.message || err.toString()))
+        .finally(() => this.refresh().catch(console.error));
+    },
     restoreConfig(e) {
       e.preventDefault();
       const file = e.currentTarget.files.item(0);