Feature: Manage password reset

• Extend LDPuser model with:
  • an "email+username" hash colum
  • a password_reset column
• Add a signal to generate this extended model instance every time a user is created
• When importing users
  • generate the hash
  • default 0/False to the password_reset column
• Add a django URL: /reinitialization?hash=thegeneratedhash
  • Add the associated view and template
  • Add a POST method associated with this view
  • On the view:
    • the value of hash should be passed in a hidden_field
    • two fields should appear, password and password_confirm
    • When POSTing, we retrieve the user from its hash (passed in the data)
    • we check if password_reset == 0, if so:
      • We update the password
      • We set the password_resetted to 1
    • else, we send an error to the user