API Tidy

- Remove old client ID queries, these are now built into the API keys. If a key has access to all clients, a client ID can be provided in the query.
- Small fixes to assets URI lookup
- Add read endpoint for vendors

api/v1/invoices/read.php

@@ -7,13 +7,11 @@ require_once '../require_get_method.php';
 
 if (isset($_GET['invoice_id'])) {
     // Invoice via ID (single)
-
     $id = intval($_GET['invoice_id']);
     $sql = mysqli_query($mysqli, "SELECT * FROM invoices WHERE invoice_id = '$id' AND invoice_client_id LIKE '$client_id'");
 
 } else {
-    // All invoices
-
+    // All invoices (by client ID if given, or all in general if key permits)
     $sql = mysqli_query($mysqli, "SELECT * FROM invoices WHERE invoice_client_id LIKE '$client_id' ORDER BY invoice_id LIMIT $limit OFFSET $offset");
 }