OAuth login and submit blocked by state

[dbirman]

• [x] When logged out blocked access to submit button (disabled at all times)

  if pn.state.user == 'guest':
  button = pn.widgets.Button(name='Login').servable(target='header')
  button.js_on_click(code='window.location.href="/login"')

• [x] Status updates should log authentication user name
• [x] Submit button protected by OAuth check
• [x] Return errors for failed submissions

[dbirman]

Need to return errors still on failed submissions and bubble up as some kind of alert warning?