Merge PR #26750 colin-fredericks/jsinput-allow-downloads

* Commits:
  feat(jsinput): Allow JSInput problems to create downloads

common/lib/capa/capa/inputtypes.py

@@ -587,6 +587,7 @@ class JSInput(InputTypeBase):
         - allow-popups
         - allow-forms
         - allow-pointer-lock
+        - allow-downloads
 
     This in turn means that the iframe cannot directly access the top-level
     window elements.

common/lib/capa/capa/templates/jsinput.html

@@ -28,7 +28,7 @@
 
   <iframe name="iframe_${id}"
       id="iframe_${id}"
-      sandbox="allow-scripts allow-popups allow-same-origin allow-forms allow-pointer-lock"
+      sandbox="allow-scripts allow-popups allow-same-origin allow-forms allow-pointer-lock allow-downloads"
       seamless="seamless"
       frameborder="0"
       src="${html_file}"

common/static/js/capa/fixtures/jsinput.html

@@ -16,7 +16,8 @@
         allow-popups
         allow-same-origin
         allow-forms
-        allow-pointer-lock"
+        allow-pointer-lock
+        allow-downloads"
       height="500"
       width="500"
       src="https://studio.edx.org/c4x/edX/DemoX/asset/webGLDemo.html">
@@ -50,4 +51,3 @@
   </div>
 </section>
 </div>
-