Registrar: undefined method `back_url' on switching registrars

[vohmar]

Trying to switch registrars in case users personal id code is associated with multiple registrars in parallel results in NoMethodError

NoMethodError in Registrar::CurrentUserController#switch
undefined method `back_url' for #Registrar::CurrentUserController:0x000056120263a4b0

  sign_in(:registrar_user, new_user)
  redirect_to :back, notice: t('.switched', new_user: new_user)
end

private

to replicate

• login to registrar portal with api user that has personal id code defined and that is shared with a users / users with associations to other registrars.
• once logged in click on user/registrar name in top right corner to open profile view with
• in linked users section click on another registrar to switch to that user
• error is returned (tested on staging and test using master branch)