Terms of service app issues

[juliusknorr]

This is a small collection of terms of service related issues found while testing with the desktop client:

• When setting up the tos app and enabling it, adding new user accounts to the client fails (this is new with tos 4.2.0)
• This started recently as with Revert "Temporarily disable the DAV plugin until clients work" terms_of_service#1018 the client started throwing an error on PROPFINDs if the terms have not been signed yet
• When the app requires to sign new terms, the desktop client opens a browser window to sign, however
  • Once that is closed there is no way to get it back
  • The UI does not indicate that the terms need to be signed in the main window (only sais offline)
  • The settings dialog for the account has a hint about terms of services but no action that could be performed

As discussed with @mgallien filing here.

Tested with terms of service 4.2.0 and desktop client 3.15.3