Allows a user to update a specific attribute (one at a time).
cognitoidentityprovider_update_user_attributes(UserAttributes,
AccessToken)
[required] An array of name-value pairs representing user attributes.
For custom attributes, you must prepend the custom:
prefix to the
attribute name.
[required] The access token for the request to update user attributes.
svc$update_user_attributes( UserAttributes = list( list( Name = "string", Value = "string" ) ), AccessToken = "string" )