I've got a dataset which I am creating via an action and database service.
I want to query the dataset when someone fills in a field and then validate
against this query.
So we have a dataset of email addresses, userA fills in their email, if it
exists in the dataset then the form should throw an error saying that they
already have done this and they don't need to do it again.
I assume this should be a formula on the email address form control but I
can't seem to get the query correct.