Do not force PDFs to be downloaded (Z#23225892) (#5994)

* Display invoice and tickets inline in browser (Z#23225892)

* Use FileResponse filename for AnswerDownload

* Use inline for PDF-view in pretix-control editor

* use as_attachment for API FileResponses

* do not ignore csp even for disposition=inline

* use as_attachment for file responses in control

* remove unused code

* improve code style

* Invoice preview inline

* do not force download on tickets in backend

* do not force download on AnswerDownload

* imrpove code style

* improve code style

* fix missing int str conversion

* Apply suggestions from code review

Co-authored-by: luelista <mira@teamwiki.de>

---------

Co-authored-by: luelista <mira@teamwiki.de>

src/pretix/presale/views/cart.py

@@ -855,9 +855,13 @@ class AnswerDownload(EventViewMixin, View):
             return Http404()
 
         ftype, _ = mimetypes.guess_type(answer.file.name)
-        resp = FileResponse(answer.file, content_type=ftype or 'application/binary')
-        resp['Content-Disposition'] = 'attachment; filename="{}-cart-{}"'.format(
+        filename = '{}-cart-{}'.format(
             self.request.event.slug.upper(),
             os.path.basename(answer.file.name).split('.', 1)[1]
-        ).encode("ascii", "ignore")
+        )
+        resp = FileResponse(
+            answer.file,
+            filename=filename,
+            content_type=ftype or 'application/binary'
+        )
         return resp