=head1 NAME

Catalyst::Plugin::Authentication::Store - All about authentication stores

=head1 MULTIPLE BACKENDS

A key issue to understand about authentication stores is that there are
potentially many of them. Each one is registered into the application, and has
a name.

For most applications, there is only one, and in this framework it is called
'default'.

When you use a plugin, like

    use Catalyst qw/
        Authentication
        Authentication::Store::Foo
    /;

the Store plugins typically only act at setup time. They rarely do more than
check out the configuration, and register e.g. Store::Foo::Backend, and set it
as the default store.

    __PACKAGE__->default_auth_store( $store );

    # the same as

    __PACKAGE__->register_auth_stores( default => $store );

=head1 WORKING WITH USERS

All credential verifiers should accept either a user object, or a user ID.

If a user ID is provided, then they will fetch the user object from the default
store, and check against it.

This should be pretty much DWIM all the time.

When you need multiple authentication backends per application then you must
fetch things yourself. For example:

    my $user = $c->get_auth_store("other_store")->get_user($id);

    $c->login( $user, $supplied_password );

Instead of just:

    $c->login( $id, $supplied_password );

which will go to the default store.

=head1 WRITING A BACKEND

Writing an authentication storage backend is a very simple matter.

The only method you really need to support is C<get_user>.

This method should accept an arbitrary list of parameters (determined by you or
the credential verifyer), and return an object inheriting
L<Catalyst::Plugin::Authentication::User>.

For introspection purposes you can also define the C<user_supports> method. See
below for optional features. This is not necessary, but might be in the future.

=head2 Integrating with Catalyst::Plugin::Session

If your users support sessions, your store should also define the
C<from_session> method. When the user object is saved in the session the
C<for_session> method is called, and that is used as the value in the session
(typically a user id). The store is also saved in the hash. If
C<<$user->store>> returns something registered, that store's name is used. If
not, the user's class is used as if it were a store (and must also support
C<from_session>).

=head2 Optional Features

Each user has the C<supports> method. For example:

    $user->supports(qw/password clear/);

should return a true value if this specific user has a clear text password.

This is on a per user (not necessarily a per store) basis. To make assumptions
about the store as a whole,

    $store->user_supports(qw/password clear/);

is supposed to be the lowest common denominator.

The standardization of these values is to be goverened by the community,
typically defined by the credential verification plugins.

=head2 Stores implying certain credentials

Sometimes a store is agnostic to the credentials (DB storage, for example), but
sometimes it isn't (like an Htpasswd file).

If you are writing a backend that wraps around a module, like
L<Catalyst::Plugin::Authentication::Store::Htpasswd> wraps around
L<Authen::Htpasswd>, it makes sense to delegate the credential checks.

This particular example caused the following "feature" to be added:

    $user->supports(qw/password self_check/);

=head2 Writing a plugin to go with the backend

Typically the backend will do the heavy lifting, by registering a store.

These plugins should look something like this:

    sub setup {
        my $c = shift;

        $c->default_auth_store(
            # a store can be an object or a class
            Catalyst::Plugin::Authentication::Store::Foo::Backend->new(
                ...
            )
        );

        $c->NEXT::setup(@_);
    }