0.2.8

Added

• A member who is signed in registers under the address on their
  membership. The registration form's E-mail field is filled in from the
  account, as Indico has always filled it in, and now carries a padlock saying
  Your STSA membership is registered under this address. So the registrations
  a member makes can always be matched back to them — and the member discount
  stays honest, because that discount is decided from the link between a
  registration and an account, and the link is made from this field.

  Any address on the account is accepted, not only the first. Indico looks a
  registration's user up with get_user_by_email, which matches secondary
  addresses too, so a member who registered under one of theirs is already
  linked to the right membership; refusing it would leave them with a
  registration they could no longer edit, because the address it already holds
  is one the form would no longer take.

  Three cases are deliberately left alone. Organizers, because adding a
  registration from the management area means typing that participant's address.
  Somebody else's registration, which is editable from the link in its
  confirmation e-mail — the person in front of it need not be the person it
  belongs to, and a member who opens one must not stamp their own address onto
  it. And invitations, whose address is the organizer's choice and which
  Indico writes into the registration whatever was submitted.

  A disabled input is a courtesy, not a rule, so the address is checked again
  wherever it actually arrives: as it is typed, when a registration is
  submitted, and when an existing one is modified. A hand-built request is
  refused the same way, with Indico's own This email address is not associated
  with your Indico account.

  The draft that carries answers across the trip to the login page now leaves
  the e-mail field out while the lock applies. Restoring the address somebody
  typed while signed out would put a value the server refuses into the one field
  they can no longer correct — and the form has already filled it in from the
  account they just signed in with, which is the address they are registering
  under anyway.

  There is a switch for it under STSA in the plugin settings,
  Register under the membership address, on by default. Switching it off
  removes the padlock and the check together.