Allow ticket QR code colour to be configured (#4726)

* Allow ticket QR code colour to be configured

This commit introduces a feature enabling users to customise the QR
code colour in the ticket editor.

* Remove redundant argument from `Dict.get` call

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

---------

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

src/pretix/base/pdf.py

@@ -822,6 +822,10 @@ class Renderer:
         kwargs = {}
         if o.get('nowhitespace', False):
             kwargs['barBorder'] = 0
+
+        if o.get('color'):
+            kwargs['barFillColor'] = Color(o['color'][0] / 255, o['color'][1] / 255, o['color'][2] / 255)
+
         qrw = QrCodeWidget(content, barLevel=level, barHeight=reqs, barWidth=reqs, **kwargs)
         d = Drawing(reqs, reqs)
         d.add(qrw)