db: fix string type incorrectly unvalidated
db: fix string type incorrectly unvalidated

We call the conversion function that expectes a NUL terminated string,
but provide a string view, which is not.

Fix by using the begin/end variant, which doesn't require a NUL terminator.

Fixes #437.

avikivity/scylla,scylladb/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,raphaelsc/scylla,avikivity/scylla,scylladb/scylla,kjniemi/scylla,raphaelsc/scylla,duarten/scylla,kjniemi/scylla,kjniemi/scylla,raphaelsc/scylla,scylladb/scylla