In order to update data, you can reference an existing subject by using its
_id or, for any predicate marked as unique as a two-tuple, i.e.
["_user/username", "jdoe"]. Predicates that you wish to update should be included as key-value pairs.
When referencing an existing subject,
"_action": "update" is inferred. Note: When updating and upserting, you can use nested transactions.
Update using a two-tuple with a unique predicate. i.e.
person/handle and relevant object:
"_id": ["person/handle", "jdoe"],
"fullName": "Jane Doe Updated"
Update using subject id:
"fullName": "Jane Doe Updated By Numeric _id"
Update Jane Doe's Handle
Write a transaction!
Using the above transaction examples, write a transaction updating Jane Doe's handle to "janieD".