Fringe QR Code Service

Usage Examples:
GET /code?text=https://example.com
GET /code?text=https://example.com&format=svg
GET /code?text=https://example.com&format=svg&w=512

Query Parameters:
- text: The text to encode in the QR code
- format: The format of the QR code (png or svg) (default png)
- w: The width of the QR code (default 256)
- ec: The error correction level (L, M, Q, H) (default M)
- margin: The margin of the QR code (default 1)