'disabled_utc' should be defined with the rest of the database fields

[tjlevel12]

Right now, disabled_utc is defined after a number of hybrid properties, which is a non-obvious location. If there's no reason for it to be down there, can we move it up with the other database fields?

keg-auth/keg_auth/model/__init__.py

Lines 100 to 110 in 0107d6c

	@is_disabled_by_date.expression
	def is_disabled_by_date(cls):
	is_disabled_expr = sa.sql.and_(
	cls.disabled_utc.isnot(None),
	cls.disabled_utc <= arrow.utcnow(),
	)
	return sa_sql.case([(is_disabled_expr, sa.true())], else_=sa.false())
	# The datetime when a user will be disabled. User will be inactive if this is set
	# to a datetime in the past.
	disabled_utc = sa.Column(ArrowType, nullable=True, default=None, server_default=sa.null())

[rsyring]

Also, is there any reason server_default is set explicitly to NULL? That should be the default.