Forms
=====

``StakingForm`` is a ``ModelForm`` with the following extras:

* An ``attachments`` field
  (:class:`~richy.core.fields.MultipleFileField`) with
  delete-while-editing support.
* The ``item`` queryset is restricted to coins
  (``Item.objects.filter(coin__isnull=False)``).
* The ``transaction`` queryset is restricted to *open*, coin-related
  transactions belonging to the current user.

Validators
----------

* ``amount`` and ``reward_amount`` must be ``>= 0``.
* ``start <= today``.
* ``start < end``.
* If a related ``transaction`` is set, ``start >= transaction.date``.