OktaProvider was dead: the provider-string const is only matched by
OAuth providers (SlackProvider in oauth2.go / connector.go), and an
API-key connector never matches on it.
Wrap the url.Parse error in nextPageURL with %w, like every sibling
driver, instead of dropping it.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>