Stop a scalar NPM response killing the request, and add certificate deletion

NPM answers a successful DELETE with the bare literal true, which vv_npm_raw() is typed to
return an array from — so deleting or toggling a proxy host has always thrown a TypeError
rather than doing the thing.

Plugin/unraid/include/auth.php

@@ -234,7 +234,17 @@ function vv_npm_raw(string $method, string $path, array $data, string $token, ar
         'code'  => (int) curl_getinfo($ch, CURLINFO_HTTP_CODE),
     ]);
     curl_close($ch);
-    return json_decode($body ?: '{}', true) ?: [];
+
+    // NPM answers a successful DELETE with the bare JSON literal `true`, not an object. This
+    // function is declared `: array`, so decoding that and returning it threw a TypeError and
+    // killed the request — which is what deleting a certificate did, and what deleting or toggling
+    // a proxy host has always done, since those three are the only callers whose endpoint answers
+    // with a scalar. Wrapped rather than returned raw, so every caller still gets an array and the
+    // outcome is readable as ['result' => true].
+    $decoded = json_decode($body ?: '{}', true);
+    if (is_array($decoded)) return $decoded;
+    if ($decoded === null)  return [];
+    return ['result' => $decoded];
 }
 
 function vv_npm_req(string $method, string $path, array $data = []): array {
@@ -261,6 +271,30 @@ function vv_npm_list_certs(): array {
     return array_values($list);
 }
 
+// Deleting a certificate is not undoable — the private key goes with it and a replacement means a
+// fresh issuance against Let's Encrypt's rate limits. The caller is expected to have checked that
+// no proxy host still points at it; NPM will happily remove one that is in use and leave the host
+// serving nothing.
+function vv_npm_delete_cert(int $id): array {
+    $r = vv_npm_req('DELETE', "/api/nginx/certificates/$id");
+    if (is_array($r) && isset($r['_err'])) return ['ok' => false, 'error' => $r['_err']];
+    // NPM answers `true` for a successful delete and an error object otherwise.
+    if (is_array($r) && isset($r['error']))
+        return ['ok' => false, 'error' => $r['error']['message'] ?? 'Delete failed'];
+    return ['ok' => true];
+}
+
+// Which proxy hosts reference a certificate. The guard that belongs with the delete above, so a
+// caller cannot forget to ask the question.
+function vv_npm_cert_users(int $id): array {
+    $p = vv_npm_list_proxies();
+    if (!($p['ok'] ?? false)) return [];
+    $out = [];
+    foreach ($p['proxies'] as $h)
+        if ((int) ($h['certificate_id'] ?? 0) === $id) $out[] = $h;
+    return $out;
+}
+
 function vv_npm_create_proxy(array $data): array {
     $r = vv_npm_req('POST', '/api/nginx/proxy-hosts', $data);
     return isset($r['id']) ? ['ok' => true, 'proxy' => $r] : ['ok' => false, 'error' => $r['error'] ?? ($r['_err'] ?? 'Create failed')];