++++++++++++++++
* The valid values for ``safe`` are:
* ``Safe.before_deploy``
* ``Safe.after_deploy``
* ``Safe.always``
Import with ``from django_safemigrate import Safe``.
``True`` is now ``Safe.before_deploy``,
and ``False`` is now ``Safe.after_deploy``.
* The default safety marking, when unspecified,
is now ``Safe.after_deploy``, instead of ``Safe.before_deploy``.
* ``Safe.always`` allows for migrations that may be run
either before or after deployment,
because they don't require any database changes.
* Multiple dependent ``Safe.after_deploy`` migrations do not block deployment
as long as there are no dependent ``Safe.before_deploy`` migrations.
* Enforce that any given value of safe is valid.