Arvados

Steps to reproduce:

• Go to a Collection's page.
• In the "Sharing and permissions" box, alternate clicking on the "Create sharing link" and "Unshare" buttons.

Sooner or later, the text in the box will fail to toggle as it should. According to the browser console, this happens because the request headers say it's returning HTML. The content is actually JavaScript, but the header means the browser doesn't execute it as expected. Ensure that this method consistently returns JavaScript as its Content-Type.