Comment 2 for bug 1859195

Re: 1., The form generation code passes the "unset username" error to the template and this has not changed with the frontend conversion to using Vanilla. Perhaps this is more of an artefact of the environment? Maybe more testing is needed.

Re: 2., I will make sure that the form submission button is disabled when the rest of the form is. (Perhaps, as a later enhancement, we can consider not showing the form at all if the user cannot add a key)