I have created an empty user meta field for a user called phone_number via the add_user_meta() function.

When I use the get_user_meta function, I can see an empty string for the meta field which is what I would expect.

But when I access the endpoint for the user via the REST API e.g. /wp-json/wp/v2/users/8, there is an empty meta array, why?

How do I update the phone_number empty meta field I created earlier via the REST API?