Tags
~~~~

Views advertise themselves to introspected menus with a ``tags`` attribute.
Well-known constants are :class:`~djcrud.tags.Tag` instances and compare equal
to their string names. Call a constant to set a ``position`` (list-style
indexing: ``0`` is first, ``-1`` is last); custom tags are plain strings, or
:class:`~djcrud.tags.Tag` when they need a position::

    import djcrud

    class Dashboard(djcrud.views.TemplateView):
        tags = djcrud.tags.NAVIGATION(position=0)

    class ReportList(djcrud.views.ListView):
        tags = djcrud.tags.Tag("reports", position=-1)

A view that belongs to several menus can mix constants, positioned copies, and
strings::

    tags = [
        djcrud.tags.NAVIGATION(position=0),
        djcrud.tags.TOPBAR,
        "reports",
    ]

:meth:`~djcrud.router.Router.get_tagged_views` places ``position >= 0`` items
at the start (``0``, then ``1``, …), unpositioned items next in declaration
order, then negative positions (``-2``, then ``-1`` last).

``djcrud_auth`` uses this to keep **Log in** first and **Log out** last::

    class LoginView(djcrud.views.FormView):
        tags = [
            djcrud.tags.TOPBAR(position=0),
            djcrud.tags.NAVIGATION(position=0),
        ]

    class LogoutView(djcrud.views.FormView):
        tags = [
            djcrud.tags.TOPBAR(position=-1),
            djcrud.tags.NAVIGATION(position=-1),
        ]

.. automodule:: djcrud.tags
   :members:
   :exclude-members: as_tags, tag_position, position_sort_key
   :member-order: bysource