Track a user's last activity

A user will have an accessedAt timestamp that will update at most once
per day if they make some API call. This timestamp can then be used
find active users and calculate daily, weekly, and monthly active users.

To ensure consistent updates to the user the $user from the resource
is always updated to the user making the request, including requests
like Create Account, Update Team Membership Status, and Create Phone
Session (confirmation). This ensures the shutdown can update the
accessedAt timestamp if there was a $user set.

src/Appwrite/Utopia/Response/Model/User.php

@@ -120,6 +120,12 @@ class User extends Model
                 'default' => new \stdClass(),
                 'example' => ['theme' => 'pink', 'timezone' => 'UTC'],
             ])
+            ->addRule('accessedAt', [
+                'type' => self::TYPE_DATETIME,
+                'description' => 'Most recent access date in ISO 8601 format.',
+                'default' => '',
+                'example' => self::TYPE_DATETIME_EXAMPLE,
+            ])
         ;
     }