Feature Request

Some channels allow end-users to download their uploaded files.

Designs

Using activity.attachments[].contentUrl to filter

Today:

• Web Chat will not allow anyone to download any uploaded files
• Direct Line channel will set "contentUrl" to a dummy URL

Tomorrow:

• Web Chat Redux store will have a helper to filter out the dummy URL from Direct Line, and set contentUrl to empty
• Web Chat will allow anyone to download any uploaded files, if the channel support it
  • activity.attachments[].contentUrl would be set to something other than falsy

[Enhancement]