update abstract method
Updates an item in the database.
NOTE: In case you want to update only one parameter of your saved object, you must pass a new copy of the object with the updated values.
Example:
await deta.base('my_base').update('my_key', {'name': 'John Doe'});
Throw DetaException
when a bad request occurs.
Implementation
Future<Map> update({required String key, required Map item});