Fix download button

[jfolk2015]

Ticket Link #1050

Description

• When api keys are requried, always validate hmac tokens on download requests
• Preserve existing functionality when api keys are not required (no token needed if public, needed if private)
• Removed add user details plugs from download pipeline because it wasn't used but will cause errors when api keys are required

Reminders:

• Be mindful of impacts of changing Major/Minor/Patch versions of each elixir app:
  • If updating patch version, are you sure there are no chart changes required to maintain functionality? If so, you should bump minor version instead.
• If changing elixir code in an "app", did you update the relevant version
  in mix.exs?