insert method Null safety
InstanceType into the underlying database.
The Query must have its values or valueMap property set. This operation will
insert a row with the data supplied in those fields to the database in context. The return value is
a Future that completes with the newly inserted
var q = Query<User>() ..values.name = "Joe"; var newUser = await q.insert();
InstanceType has properties with Validate metadata, those validations
will be executed prior to sending the query to the database.