I need a small, code addition for WHMCS that adds a dynamic nameserver selector to /cart.php?a=confdomains. See attached image for detail. What the dropdown must do • Always show “Reset to default” first. • Then list each unique nameserver set that belongs to my customer’s active hosting packages—no duplicates, no suspended or cancelled services. In practice most accounts only carry one or two packages, so the list will stay short. Behaviour • When the user chooses a set, any values present in the five native nameserver input boxes are instantly cleared and replaced with the chosen set. • If “Reset to default” is picked, the five boxes become blank again. Technical notes • Clean, human-readable PHP and JavaScript (vanilla JS). • Hook or override must survive core updates; a template override or client-area hook is preferred over editing core files. • All inline comments and code in English. Deliverable 1. Ready-to-drop-in hook/file(s) plus any template edits. 2. Brief install steps so I can replicate on staging and production.